【简答题】阅读理解。 Bill Clinton took office (就职) on January 20th, 1993 and became the 42nd U.S. president (总统). He is the first U.S. president who was born after World War II (第二次). He is also one of the young...
【单选题】When scientists first warned in the 1970s that CFCs could attack ozone, the U.S. responded by banning their use in spray cans. But the rest of the world continued to use CFC -based aerosol cans, and o...
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 chlorine.