It was once thought that air pollution affected only the areas immediately around large cities with

14. The underlined word “offset” in Para. 2 could best be replaced by “________”.
A. slip into B. make up for C. set up D. catch up with
15. It can be learned from the passage that ________.
A. lowering the world’s temperature merely a few degrees would lead many major farming areas to disaster
B. raising the world’s temperature only a few degrees would not do much harm to life on earth
C. almost no temperature variations have occurred over the past decade
D. the world’s temperature will remain constant(永恒的，不变的)in the years to come

答案DBBA