A．many industrialists feel no concern for the improvement of pollution control
B．breathing low concentrations of urban dust does not necessarily sicken or kill people
C．no acceptable biological mechanism has been suggested to explain the toxicity of low concentration of urban dust
D．scientists have done nothing to reveal the mystery of the toxicity of low concentration of urban dust

A．how inhaled dust harms the lungs
B．the function of Environmental Protection Agency
C．the function of human alveolar macrophages
D．studies by Environmental Protection Agency

A．Objective.
B．Mechanical.
C．Superficial.
D．Paradoxical.

A．They stressed photography was a means of making people happy.
B．It was art for recording the world.
C．It was a device for observing the world impartially.
D．It was an art comparable to painting.

A．defining the Modernist attitude toward art
B．explaining how photography emerged as a fine art
C．explaining the attitude of serious contemporary photographers toward photography as art and placing those attitudes in their historical context
D．defining the various approaches that serious contemporary photographers take toward their art and assessing the value of each of those approaches

A．He wants to provide an example of artists who, like serious contemporary photographers, disavowed traditionally accepted aims of modem art.
B．Be wants to set forth an analogy between the Abstract Expressionist painters and classical Modernist painters.
C．He wants to provide a contrast to Pop artist and others.
D．He wants to provide an explanation of why serious photography, like other contemporary visual forms, is not an should not pretend to be an art.

A．make active again
B．study again
C．go over again
D．find the value again

A．people had to do the productive work at home
B．people were forced to look elsewhere for means of supporting themselves
C．people were able to be dependent on their land
D．people were badly paid for the work they managed to find

A．universal employment virtually guaranteed prosperity
B．economic freedom came within everyone’s grasp
C．patterns of work were fundamentally changed
D．people’s attitudes to work had to be reversed

A．the work status of those not in paid employment suffered
B．the household and village community disappeared completely
C．men now traveled enormous distances to their places of work
D．young and old people became superfluous components of society