问题
选择题
A large number of engineers _____ to Africa by our government to help the people there every year.[ ]
A. have sent
B. will send
C. are sent
答案
答案：C
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A large number of engineers _____ to Africa by our government to help the people there every year.[ ]
A. have sent
B. will send
C. are sent
答案：C
2NO2（气）+热量，不能说明已达到平衡状态的是[ ]