False teeth have been found in Italy in human heads that are over 2，500 years old. They were made of bone and set in gold. However，for hundreds of years afterwards，the apparent dental skill of those early people was lost. Without false teeth people looked old before their time，since so many lost their teeth at an early age.
Toward the end of the 17th century，rich people could buy false teeth made from ivory. The teeth were tied together with silk thread，but it was difficult to keep them in the mouth. That was why rich people would rather buy teeth from the poor who would often sell their teeth to buy food and clothing.
Early in the 18th century a French doctor used steel springs to hold teeth in place. However，it was difficult to close one‘s mouth！ Late in the same century porcelain （瓷）teeth set in gold were often used to make false teeth.
Although the use of artificial teeth increased，human teeth continued to be used also. In the 19th century，teeth from soldiers killed in battle were made into artificial teeth. For example，teeth from the dead in the American Civil War were sent to England.
By the middle of the 19th century，an American doctor，Claudius Ash，invented a better kind of porcelain tooth made of a special kind of hard rubber.

False teeth have been found in Italy in human heads that are over 2，500 years old. They were made of bone and set in gold. However，for hundreds of years afterwards，the apparent dental skill of those early people was lost. Without false teeth people looked old before their time，since so many lost their teeth at an early age.
Toward the end of the 17th century，rich people could buy false teeth made from ivory. The teeth were tied together with silk thread，but it was difficult to keep them in the mouth. That was why rich people would rather buy teeth from the poor who would often sell their teeth to buy food and clothing.
Early in the 18th century a French doctor used steel springs to hold teeth in place. However，it was difficult to close one‘s mouth！ Late in the same century porcelain （瓷）teeth set in gold were often used to make false teeth.
Although the use of artificial teeth increased，human teeth continued to be used also. In the 19th century，teeth from soldiers killed in battle were made into artificial teeth. For example，teeth from the dead in the American Civil War were sent to England.
By the middle of the 19th century，an American doctor，Claudius Ash，invented a better kind of porcelain tooth made of a special kind of hard rubber.

False teeth have been found in Italy in human heads that are over 2，500 years old. They were made of bone and set in gold. However，for hundreds of years afterwards，the apparent dental skill of those early people was lost. Without false teeth people looked old before their time，since so many lost their teeth at an early age.
Toward the end of the 17th century，rich people could buy false teeth made from ivory. The teeth were tied together with silk thread，but it was difficult to keep them in the mouth. That was why rich people would rather buy teeth from the poor who would often sell their teeth to buy food and clothing.
Early in the 18th century a French doctor used steel springs to hold teeth in place. However，it was difficult to close one‘s mouth！ Late in the same century porcelain （瓷）teeth set in gold were often used to make false teeth.
Although the use of artificial teeth increased，human teeth continued to be used also. In the 19th century，teeth from soldiers killed in battle were made into artificial teeth. For example，teeth from the dead in the American Civil War were sent to England.
By the middle of the 19th century，an American doctor，Claudius Ash，invented a better kind of porcelain tooth made of a special kind of hard rubber.

False teeth have been found in Italy in human heads that are over 2，500 years old. They were made of bone and set in gold. However，for hundreds of years afterwards，the apparent dental skill of those early people was lost. Without false teeth people looked old before their time，since so many lost their teeth at an early age.
Toward the end of the 17th century，rich people could buy false teeth made from ivory. The teeth were tied together with silk thread，but it was difficult to keep them in the mouth. That was why rich people would rather buy teeth from the poor who would often sell their teeth to buy food and clothing.
Early in the 18th century a French doctor used steel springs to hold teeth in place. However，it was difficult to close one‘s mouth！ Late in the same century porcelain （瓷）teeth set in gold were often used to make false teeth.
Although the use of artificial teeth increased，human teeth continued to be used also. In the 19th century，teeth from soldiers killed in battle were made into artificial teeth. For example，teeth from the dead in the American Civil War were sent to England.
By the middle of the 19th century，an American doctor，Claudius Ash，invented a better kind of porcelain tooth made of a special kind of hard rubber.

For many years ，T-shirts were simple short-sleeved undershirts for men and boys. T-shirts used to be of one color－white. And since they were worn under shirts，they were generally not seen.
Today the T-shirt has become fashionable. It can be seen everywhere and on everyone. Women and little children wear T-shirts as do teenagers，university students，and men from all walks of life （各行各业）。T-shirts are worn on playground，at the beach or in town. They can also be worn for work. Yet T-shirts remain relatively inexpensive and long wearing，as well as easy to care for. Smart but comfortable and convenient to wear，they have become one of American‘s newest ideas on fashion.
Although T-shirts are now available in a wide variety of bright materials and styles，the most popular kind is the traditional cotton T-shirts with a slogan or picture printed on the front. A T-shirt may bear a picture，a single word，a popular phrase，or an advertisement. As T-shirts are becoming more and more popular，new designs are coming up all the time.

For many years ，T-shirts were simple short-sleeved undershirts for men and boys. T-shirts used to be of one color－white. And since they were worn under shirts，they were generally not seen.
Today the T-shirt has become fashionable. It can be seen everywhere and on everyone. Women and little children wear T-shirts as do teenagers，university students，and men from all walks of life （各行各业）。T-shirts are worn on playground，at the beach or in town. They can also be worn for work. Yet T-shirts remain relatively inexpensive and long wearing，as well as easy to care for. Smart but comfortable and convenient to wear，they have become one of American‘s newest ideas on fashion.
Although T-shirts are now available in a wide variety of bright materials and styles，the most popular kind is the traditional cotton T-shirts with a slogan or picture printed on the front. A T-shirt may bear a picture，a single word，a popular phrase，or an advertisement. As T-shirts are becoming more and more popular，new designs are coming up all the time.

For many years ，T-shirts were simple short-sleeved undershirts for men and boys. T-shirts used to be of one color－white. And since they were worn under shirts，they were generally not seen.
Today the T-shirt has become fashionable. It can be seen everywhere and on everyone. Women and little children wear T-shirts as do teenagers，university students，and men from all walks of life （各行各业）。T-shirts are worn on playground，at the beach or in town. They can also be worn for work. Yet T-shirts remain relatively inexpensive and long wearing，as well as easy to care for. Smart but comfortable and convenient to wear，they have become one of American‘s newest ideas on fashion.
Although T-shirts are now available in a wide variety of bright materials and styles，the most popular kind is the traditional cotton T-shirts with a slogan or picture printed on the front. A T-shirt may bear a picture，a single word，a popular phrase，or an advertisement. As T-shirts are becoming more and more popular，new designs are coming up all the time.

Passage One
Questions 21 to 25 are based on the following passage.
For many years ，T-shirts were simple short-sleeved undershirts for men and boys. T-shirts used to be of one color－white. And since they were worn under shirts，they were generally not seen.
Today the T-shirt has become fashionable. It can be seen everywhere and on everyone. Women and little children wear T-shirts as do teenagers，university students，and men from all walks of life （各行各业）。T-shirts are worn on playground，at the beach or in town. They can also be worn for work. Yet T-shirts remain relatively inexpensive and long wearing，as well as easy to care for. Smart but comfortable and convenient to wear，they have become one of American‘s newest ideas on fashion.
Although T-shirts are now available in a wide variety of bright materials and styles，the most popular kind is the traditional cotton T-shirts with a slogan or picture printed on the front. A T-shirt may bear a picture，a single word，a popular phrase，or an advertisement. As T-shirts are becoming more and more popular，new designs are coming up all the time.

For many years ，T-shirts were simple short-sleeved undershirts for men and boys. T-shirts used to be of one color－white. And since they were worn under shirts，they were generally not seen.
Today the T-shirt has become fashionable. It can be seen everywhere and on everyone. Women and little children wear T-shirts as do teenagers，university students，and men from all walks of life （各行各业）。T-shirts are worn on playground，at the beach or in town. They can also be worn for work. Yet T-shirts remain relatively inexpensive and long wearing，as well as easy to care for. Smart but comfortable and convenient to wear，they have become one of American‘s newest ideas on fashion.
Although T-shirts are now available in a wide variety of bright materials and styles，the most popular kind is the traditional cotton T-shirts with a slogan or picture printed on the front. A T-shirt may bear a picture，a single word，a popular phrase，or an advertisement. As T-shirts are becoming more and more popular，new designs are coming up all the time.

Lightening and thunder seem very different from fog，clouds，rain，wind，heat，and other things which make up the weather.（11）without knowing about the rest of the（12），one cannot understand lightening and thunder. Long ago，（13）scientists had begun to study the weather，everyone was afraid of lightening and thunder. （14）the ancient Greeks and Romans，thunder was the angry voice of （15）great god Zeus，or Jupiter.
Today we know more about weather and （16）lightening and thunder too，though there（17） still much to be learned. People today are not often afraid of thunderstorms，though we know that lightening （18）dangerous. （19）we understand lightening and thunder，there is a thrill （激动） in watching a summer thunderstorm which clears the air and leaves us（20）.