单项选择题

A．Because the CFCs directly damage the people's health.……

Why should governments ensure tire careful handling and recycling of the CFCs now in use

A．Because the CFCs directly damage the people's health.
B．Because the CFCs are poisonous chemicals.
C．Because the production of the CFCs costs a lot.
D．Because the CFCs can attack ozone by liberating atoms of chlorin

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热门试题

单项选择题At first, locomotives could not popularize themselves because they ______.

A．could not bring profits or save much labor
B．attract people
C．only caught some people's interest
D．were not welcome

单项选择题The multi-tube boiler system made the Rocket, Robert's locomotive,______.

A．powerful
B．achieve a speed of 30 miles an hour
C．acquire 25 little tubes
D．good for hauling trains

单项选择题According to the passage, what do student researchers often learn when they discuss their work in class

A．Other students rarely have objective comments about it.
B．Other students do not believe the researchers did the work themselves.
C．Some students feel that the conclusions are too obvious.
D．Some students do not understand the meaning of the researchers’ questions.

单项选择题According to the passage, what is one major criticism students often make of published research

A．The research has been done in unimportant fields.
B．The researchers did not adequately establish the relationships involved.
C．The researchers failed to provide an appropriate summary.
D．The research has not been written in an interesting way.

单项选择题What does the author think about trying to find weaknesses in other people's research

A．It should only be attempted by experienced researchers.
B．It may cause researchers to avoid publishing good work.
C．It is currently being done to excess.
D．It can be useful in planning future researc