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 5 ______

单项选择题The upper class is also called the out-of-sight class because______.

单项选择题In the future robots will also ______.

单项选择题The sonar devices must be placed ().

A. from time to time
B. after the undersea vehicle dives
C. at the time when the undersea vehicle is diving
D. before the undersea vehicle dives

填空题E

单项选择题52（）

A. Apart from
B. However
C. In addition
D. As well