A. Atmospheric Scientists
B. The Calculations Made at the Berlin Workshop
C. The Previous Calculations of the Effect of Aerosols
D. The Scientists’ Agreement
E. The Authoritative Conclusion
F. Greenhouse Gases
Paragraph 3 ______

单项选择题By more challenging (Para. 6), the author means ().

A. more interesting
B. more demanding
C. more attractive
D. more’dangerous

填空题Paragraph 2 ______

单项选择题Cutting trees to grow more food may hamper a developing country in its fight against poverty.()

A. Right
B. Wrong
C. Not mentioned

单项选择题51（）

A.built
B.designed
C.intended
D.lined

单项选择题The “old rich” get richer______