American farmers have been complaining of labor shortages for several years.The complaints are unlikely to stop without an overhaul of immigration rules for farm works.
　　Congress has obstructed efforts to create a more straightforward visa for agricultural workers that would let foreign workers stay longer in the U.S. and change jobs within the industry.If this doesn’t change.American businesses.communities, and consumers will be the losers.
　　Perhaps half of U.S. farm laborers are undocumented immigrants. As fewer such workers enter the country, the characteristics of the agricultural workforce are changing. Today's farm laborers, while still predominantly born in Mexico, are more likely to be settled rather than migrating and more likely to be married than single, They're also aging. At the start of this century, about one-third of crop workers were over the age of 35. Now more than half are. And picking crops is hard on older bodies. One oft-debated cure for this labor shortage remains as implausible as it's been all along: Native U.S. workers won't be returning to the farm.
　　Mechanization is not the answer either—not yet, at least. Production of com,cotton, rice, soybeans, and wheat has been largely mechanized, but many high-value, labor-intensive crops, such as strawberries, need labor. Even dairy farms,where robots do a small share of milking, have a long way to go before they ' re automated.
　　As a result, farms have grown increasingly reliant on temporary guest workers using the H-2A visa to fill the gaps in the workforce. Starting around 2012, requests for the visas rose sharply; from 2011 to 2016 the number of visas issued more than doubled.
The H-2A visa has no numerical cap, unlike the H-2B visa for nonagricultural work which is limited to 66,000 a year. Even so, employers complain they aren’t given all the workers they need.The process is cumbersome,expensive,and unreliable. One survey found that bureaucratic delays led the average H-2A worker to arrive on the job 22 days late. The shortage is compounded by federal immigration raids, which remove some workers and drive others underground.
In a 2012 survey, 71 percent of tree-fruit growers and nearly 80 percent of raisin and berry growers said they were short of labor. Some western growers have responded by moving operations to Mexico. From 1998-2000, 14.5 percent of the fruit Americans consumed was imported. Little more than a decade later, the share of imported fruit had increased to 25.8 percent.
In effect, the U.S. can import food or it can import the workers who pick it.

What is the much-argued solution to the labor shortage in U.S farming?（）

American farmers have been complaining of labor shortages for several years.The complaints are unlikely to stop without an overhaul of immigration rules for farm works.
　　Congress has obstructed efforts to create a more straightforward visa for agricultural workers that would let foreign workers stay longer in the U.S. and change jobs within the industry.If this doesn’t change.American businesses.communities, and consumers will be the losers.
　　Perhaps half of U.S. farm laborers are undocumented immigrants. As fewer such workers enter the country, the characteristics of the agricultural workforce are changing. Today's farm laborers, while still predominantly born in Mexico, are more likely to be settled rather than migrating and more likely to be married than single, They're also aging. At the start of this century, about one-third of crop workers were over the age of 35. Now more than half are. And picking crops is hard on older bodies. One oft-debated cure for this labor shortage remains as implausible as it's been all along: Native U.S. workers won't be returning to the farm.
　　Mechanization is not the answer either—not yet, at least. Production of com,cotton, rice, soybeans, and wheat has been largely mechanized, but many high-value, labor-intensive crops, such as strawberries, need labor. Even dairy farms,where robots do a small share of milking, have a long way to go before they ' re automated.
　　As a result, farms have grown increasingly reliant on temporary guest workers using the H-2A visa to fill the gaps in the workforce. Starting around 2012, requests for the visas rose sharply; from 2011 to 2016 the number of visas issued more than doubled.
The H-2A visa has no numerical cap, unlike the H-2B visa for nonagricultural work which is limited to 66,000 a year. Even so, employers complain they aren’t given all the workers they need.The process is cumbersome,expensive,and unreliable. One survey found that bureaucratic delays led the average H-2A worker to arrive on the job 22 days late. The shortage is compounded by federal immigration raids, which remove some workers and drive others underground.
In a 2012 survey, 71 percent of tree-fruit growers and nearly 80 percent of raisin and berry growers said they were short of labor. Some western growers have responded by moving operations to Mexico. From 1998-2000, 14.5 percent of the fruit Americans consumed was imported. Little more than a decade later, the share of imported fruit had increased to 25.8 percent.
In effect, the U.S. can import food or it can import the workers who pick it.

One trouble with U.S. agricultural workforce is（）

American farmers have been complaining of labor shortages for several years.The complaints are unlikely to stop without an overhaul of immigration rules for farm works.
　　Congress has obstructed efforts to create a more straightforward visa for agricultural workers that would let foreign workers stay longer in the U.S. and change jobs within the industry.If this doesn’t change.American businesses.communities, and consumers will be the losers.
　　Perhaps half of U.S. farm laborers are undocumented immigrants. As fewer such workers enter the country, the characteristics of the agricultural workforce are changing. Today's farm laborers, while still predominantly born in Mexico, are more likely to be settled rather than migrating and more likely to be married than single, They're also aging. At the start of this century, about one-third of crop workers were over the age of 35. Now more than half are. And picking crops is hard on older bodies. One oft-debated cure for this labor shortage remains as implausible as it's been all along: Native U.S. workers won't be returning to the farm.
　　Mechanization is not the answer either—not yet, at least. Production of com,cotton, rice, soybeans, and wheat has been largely mechanized, but many high-value, labor-intensive crops, such as strawberries, need labor. Even dairy farms,where robots do a small share of milking, have a long way to go before they ' re automated.
　　As a result, farms have grown increasingly reliant on temporary guest workers using the H-2A visa to fill the gaps in the workforce. Starting around 2012, requests for the visas rose sharply; from 2011 to 2016 the number of visas issued more than doubled.
The H-2A visa has no numerical cap, unlike the H-2B visa for nonagricultural work which is limited to 66,000 a year. Even so, employers complain they aren’t given all the workers they need.The process is cumbersome,expensive,and unreliable. One survey found that bureaucratic delays led the average H-2A worker to arrive on the job 22 days late. The shortage is compounded by federal immigration raids, which remove some workers and drive others underground.
In a 2012 survey, 71 percent of tree-fruit growers and nearly 80 percent of raisin and berry growers said they were short of labor. Some western growers have responded by moving operations to Mexico. From 1998-2000, 14.5 percent of the fruit Americans consumed was imported. Little more than a decade later, the share of imported fruit had increased to 25.8 percent.
In effect, the U.S. can import food or it can import the workers who pick it.

What problem should be addressed according to the first two paragraphs?（）

　Forests give us shade, quiet and one of the harder challenges in the fight against climate change. Even as we humans count on forests to soak up a good share of the carbon dioxide we produce, we are threatening their ability to do so.The climate change we are hastening could one day leave us with forests that emit more carbon than they absorb.
　　Thankfully, there is a way out of this trap . but it involves striking a subtle balance. Helping forests flourish as valuable"carbon sinks" long into the future may require reducing their capacity to absorb carbon now, California is leading the way,as it does on so many climate efforts, in figuring out the details.
　　The state's proposed Forest Carbon Plan aims to double efforts to thin out young trees and clear brush in parts of the forest. This temporarily lowers carbon-carrying capacity. But the remaining trees draw a greater share of the available moisture, so they grow and thrive, restoring the forest's capacity to pull carbon from the air. Healthy trees are also better able to fend off insects. The landscape is rendered less easily burnable. Even in the event of a fire, fewer trees are consumed.
　　The need for such planning is increasingly urgent. Already, since 2010,drought and insects have killed over 100million trees in California, most of them in 2016 alone, and wildfires have burned hundreds of thousands of acres.
　　California plans to treat 35,000 acres of forest a year by 2020, and 60,00 by 2030- financed from the proceeds of the state' s emissions- permit auctions, That's only a small share of the total acreage that could benefit, about half a million acres in all, so it will be vital to prioritize areas at greatest risk of fire or drought.
　　The strategy also aims to ensure that carbon in woody material removed from the forests is locked away in the form of solid lumber or burned as biofuel in vehicles that would otherwise run on fossil fuels. New research on transportation biofuels is already under way.
State governments are well accustomed to managing forests, but traditionally they've focused on wildlife, watersheds and opportunities for recreation. Only recently have they come to see the vital part forests will have to play in storing carbon. Califormia's plan, which is expected to be finalized by the governor next year, should serve as a model.

The author's attitude to California's plan can best be described as（）.

　Forests give us shade, quiet and one of the harder challenges in the fight against climate change. Even as we humans count on forests to soak up a good share of the carbon dioxide we produce, we are threatening their ability to do so.The climate change we are hastening could one day leave us with forests that emit more carbon than they absorb.
　　Thankfully, there is a way out of this trap . but it involves striking a subtle balance. Helping forests flourish as valuable"carbon sinks" long into the future may require reducing their capacity to absorb carbon now, California is leading the way,as it does on so many climate efforts, in figuring out the details.
　　The state's proposed Forest Carbon Plan aims to double efforts to thin out young trees and clear brush in parts of the forest. This temporarily lowers carbon-carrying capacity. But the remaining trees draw a greater share of the available moisture, so they grow and thrive, restoring the forest's capacity to pull carbon from the air. Healthy trees are also better able to fend off insects. The landscape is rendered less easily burnable. Even in the event of a fire, fewer trees are consumed.
　　The need for such planning is increasingly urgent. Already, since 2010,drought and insects have killed over 100million trees in California, most of them in 2016 alone, and wildfires have burned hundreds of thousands of acres.
　　California plans to treat 35,000 acres of forest a year by 2020, and 60,00 by 2030- financed from the proceeds of the state' s emissions- permit auctions, That's only a small share of the total acreage that could benefit, about half a million acres in all, so it will be vital to prioritize areas at greatest risk of fire or drought.
　　The strategy also aims to ensure that carbon in woody material removed from the forests is locked away in the form of solid lumber or burned as biofuel in vehicles that would otherwise run on fossil fuels. New research on transportation biofuels is already under way.
State governments are well accustomed to managing forests, but traditionally they've focused on wildlife, watersheds and opportunities for recreation. Only recently have they come to see the vital part forests will have to play in storing carbon. Califormia's plan, which is expected to be finalized by the governor next year, should serve as a model.

What is essential to California's plan according to Paragraph 5?（）

　Forests give us shade, quiet and one of the harder challenges in the fight against climate change. Even as we humans count on forests to soak up a good share of the carbon dioxide we produce, we are threatening their ability to do so.The climate change we are hastening could one day leave us with forests that emit more carbon than they absorb.
　　Thankfully, there is a way out of this trap . but it involves striking a subtle balance. Helping forests flourish as valuable"carbon sinks" long into the future may require reducing their capacity to absorb carbon now, California is leading the way,as it does on so many climate efforts, in figuring out the details.
　　The state's proposed Forest Carbon Plan aims to double efforts to thin out young trees and clear brush in parts of the forest. This temporarily lowers carbon-carrying capacity. But the remaining trees draw a greater share of the available moisture, so they grow and thrive, restoring the forest's capacity to pull carbon from the air. Healthy trees are also better able to fend off insects. The landscape is rendered less easily burnable. Even in the event of a fire, fewer trees are consumed.
　　The need for such planning is increasingly urgent. Already, since 2010,drought and insects have killed over 100million trees in California, most of them in 2016 alone, and wildfires have burned hundreds of thousands of acres.
　　California plans to treat 35,000 acres of forest a year by 2020, and 60,00 by 2030- financed from the proceeds of the state' s emissions- permit auctions, That's only a small share of the total acreage that could benefit, about half a million acres in all, so it will be vital to prioritize areas at greatest risk of fire or drought.
　　The strategy also aims to ensure that carbon in woody material removed from the forests is locked away in the form of solid lumber or burned as biofuel in vehicles that would otherwise run on fossil fuels. New research on transportation biofuels is already under way.
State governments are well accustomed to managing forests, but traditionally they've focused on wildlife, watersheds and opportunities for recreation. Only recently have they come to see the vital part forests will have to play in storing carbon. Califormia's plan, which is expected to be finalized by the governor next year, should serve as a model.

California's Forest Carbon Plan endeavors to （）

　Forests give us shade, quiet and one of the harder challenges in the fight against climate change. Even as we humans count on forests to soak up a good share of the carbon dioxide we produce, we are threatening their ability to do so.The climate change we are hastening could one day leave us with forests that emit more carbon than they absorb.
　　Thankfully, there is a way out of this trap . but it involves striking a subtle balance. Helping forests flourish as valuable"carbon sinks" long into the future may require reducing their capacity to absorb carbon now, California is leading the way,as it does on so many climate efforts, in figuring out the details.
　　The state's proposed Forest Carbon Plan aims to double efforts to thin out young trees and clear brush in parts of the forest. This temporarily lowers carbon-carrying capacity. But the remaining trees draw a greater share of the available moisture, so they grow and thrive, restoring the forest's capacity to pull carbon from the air. Healthy trees are also better able to fend off insects. The landscape is rendered less easily burnable. Even in the event of a fire, fewer trees are consumed.
　　The need for such planning is increasingly urgent. Already, since 2010,drought and insects have killed over 100million trees in California, most of them in 2016 alone, and wildfires have burned hundreds of thousands of acres.
　　California plans to treat 35,000 acres of forest a year by 2020, and 60,00 by 2030- financed from the proceeds of the state' s emissions- permit auctions, That's only a small share of the total acreage that could benefit, about half a million acres in all, so it will be vital to prioritize areas at greatest risk of fire or drought.
　　The strategy also aims to ensure that carbon in woody material removed from the forests is locked away in the form of solid lumber or burned as biofuel in vehicles that would otherwise run on fossil fuels. New research on transportation biofuels is already under way.
State governments are well accustomed to managing forests, but traditionally they've focused on wildlife, watersheds and opportunities for recreation. Only recently have they come to see the vital part forests will have to play in storing carbon. Califormia's plan, which is expected to be finalized by the governor next year, should serve as a model.

To maintain forests as valuable "carbon sinks," we may need to（）

　Forests give us shade, quiet and one of the harder challenges in the fight against climate change. Even as we humans count on forests to soak up a good share of the carbon dioxide we produce, we are threatening their ability to do so.The climate change we are hastening could one day leave us with forests that emit more carbon than they absorb.
　　Thankfully, there is a way out of this trap . but it involves striking a subtle balance. Helping forests flourish as valuable"carbon sinks" long into the future may require reducing their capacity to absorb carbon now, California is leading the way,as it does on so many climate efforts, in figuring out the details.
　　The state's proposed Forest Carbon Plan aims to double efforts to thin out young trees and clear brush in parts of the forest. This temporarily lowers carbon-carrying capacity. But the remaining trees draw a greater share of the available moisture, so they grow and thrive, restoring the forest's capacity to pull carbon from the air. Healthy trees are also better able to fend off insects. The landscape is rendered less easily burnable. Even in the event of a fire, fewer trees are consumed.
　　The need for such planning is increasingly urgent. Already, since 2010,drought and insects have killed over 100million trees in California, most of them in 2016 alone, and wildfires have burned hundreds of thousands of acres.
　　California plans to treat 35,000 acres of forest a year by 2020, and 60,00 by 2030- financed from the proceeds of the state' s emissions- permit auctions, That's only a small share of the total acreage that could benefit, about half a million acres in all, so it will be vital to prioritize areas at greatest risk of fire or drought.
　　The strategy also aims to ensure that carbon in woody material removed from the forests is locked away in the form of solid lumber or burned as biofuel in vehicles that would otherwise run on fossil fuels. New research on transportation biofuels is already under way.
State governments are well accustomed to managing forests, but traditionally they've focused on wildlife, watersheds and opportunities for recreation. Only recently have they come to see the vital part forests will have to play in storing carbon. Califormia's plan, which is expected to be finalized by the governor next year, should serve as a model.

By saying "one of the harder challenges ,"the author implies that（）
 

　　Unlike so-called basic emotions such as sadness, fear, and anger, guilt emerges a little later, in conjunction with a child's growing grasp of social and moral norms. Children aren't born knowing how to say "I'm sorry”; rather, they learn over time that such statements appease parents and friends - and their own consciences. This is why researchers generally regard so-called moral guilt, in the right amount, to be a good thing.
　　In the popular imagination, of course, guilt still gets a bad rap. It is deeply uncomfortable - it's the emotional equivalent of wearing a jacket weighted with stones. Yet this understanding is outdated. "There has been a kind of revival or a rethinking about what guilt is and what role guilt can serve," says Amrisha Vaish, a psychology researcher at the University of Virginia, adding that this revival is part of a larger recognition that emotions aren't binary -feelings that may be advantageous in one context may be harmful in another. Jealousy and anger, for example, may have evolved to alert us to important inequalities. Too much happiness can be destructive.
　　And guilt, by prompting us to think more deeply about our goodness, can encourage humans to make up for errors and fix relationships. Guilt, in other words, can help hold a cooperative species together. It is a kind of social glue.
　　Viewed in this light, guilt is an opportunity. Work by Tina Malti, a psychology professor at the University of Toronto, suggests that guilt may compensate for an emotional deficiency. In a number of studies, Malti and others have shown that guilt and sympathy may represent different pathways to cooperation and sharing Some kids who are low in sympathy may make up for that shortfall by experiencing more guilt, which can rein in their nastier impulses. And vice versa: High sympathy can substitute for low guilt.
　　In a 2014 study, for example, Malti looked at 244 children Using caregiver assessments and the children's self-observations, she rated each child's overall sympathy level and his or her tendency to feel negative emotions after moral transgressions. Then the kids were handed chocolate coins, and given a chance to shared them with an anonymous child. For the low-sympathy kids, how much they shared appeared to turn on how inclined they were to feel guilty. The guilt-prone ones shared more, even though they hadn't magically become more sympathetic to the other child's deprivation
　　" That's good news, " Malti says. " We can be prosocial because we caused harm and we feel regret.”

The word "transgressions" (Line 4, Para. 5) is closest in meaning to（）
 

　　Unlike so-called basic emotions such as sadness, fear, and anger, guilt emerges a little later, in conjunction with a child's growing grasp of social and moral norms. Children aren't born knowing how to say "I'm sorry”; rather, they learn over time that such statements appease parents and friends - and their own consciences. This is why researchers generally regard so-called moral guilt, in the right amount, to be a good thing.
　　In the popular imagination, of course, guilt still gets a bad rap. It is deeply uncomfortable - it's the emotional equivalent of wearing a jacket weighted with stones. Yet this understanding is outdated. "There has been a kind of revival or a rethinking about what guilt is and what role guilt can serve," says Amrisha Vaish, a psychology researcher at the University of Virginia, adding that this revival is part of a larger recognition that emotions aren't binary -feelings that may be advantageous in one context may be harmful in another. Jealousy and anger, for example, may have evolved to alert us to important inequalities. Too much happiness can be destructive.
　　And guilt, by prompting us to think more deeply about our goodness, can encourage humans to make up for errors and fix relationships. Guilt, in other words, can help hold a cooperative species together. It is a kind of social glue.
　　Viewed in this light, guilt is an opportunity. Work by Tina Malti, a psychology professor at the University of Toronto, suggests that guilt may compensate for an emotional deficiency. In a number of studies, Malti and others have shown that guilt and sympathy may represent different pathways to cooperation and sharing Some kids who are low in sympathy may make up for that shortfall by experiencing more guilt, which can rein in their nastier impulses. And vice versa: High sympathy can substitute for low guilt.
　　In a 2014 study, for example, Malti looked at 244 children Using caregiver assessments and the children's self-observations, she rated each child's overall sympathy level and his or her tendency to feel negative emotions after moral transgressions. Then the kids were handed chocolate coins, and given a chance to shared them with an anonymous child. For the low-sympathy kids, how much they shared appeared to turn on how inclined they were to feel guilty. The guilt-prone ones shared more, even though they hadn't magically become more sympathetic to the other child's deprivation
　　" That's good news, " Malti says. " We can be prosocial because we caused harm and we feel regret.”

Malti and others have shown that cooperation and sharing（）