1. As pointed out at the beginning of the passage, people used to think that air pollution＿＿＿
　　[A] caused widespread damage in the countryside
　　[B] affected the entire eastern half of the United States
　　[C] had damaged effect on health
　　[D] existed merely in urban and industries areas
　　2. As to the greenhouse effect, the author＿＿＿
　　[A] shares the same view with the scientists
　　[B] is uncertain of its occurrence
　　[C] rejects it as being ungrounded
　　[D] thinks that it will destroy the world soon
　　3. The word "offset" in the second paragraph could be replaced by＿＿＿
　　[A] slip into
　　[B] make up for
　　[C] set up
　　[D] cath up with
　　4. It can be concluded that＿＿＿
　　[A] raising the world's temperature only a few degrees would not do much harm to life　on earth
　　[B] lowering the world's temperature merely a few degrees would lead many majoy
　　farming areas to disaster
　　[C] almost no temperature variations have occurred over the past decade
　　[D] the world' s temperature will remain constant in the years to come
　　5. This passage is primarily about＿＿＿
　　[A] the greenhouse effect
　　[B] the burning of fossil fuels
　　[C] the potential effect of air pollution
　　[D] the likelihood of a new ice age