一对称配筋的大偏心受压构件，承受的四组内力中，最不利的一组内力(配筋最多的)为：（）。
A. M=500kN·m，N=200kN；
B. M=491kN·m，N=304kN；
C. M=503kN·m，N=398kN；
D. M=－512kN·m，N=506kN。
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It is necessary that a college student __________ a foreign language.
A. should master
B. be mastered
C. mastered
D. should mastering
He took his raincoat with him in case it __________.
A. rain
B. should rain
C. rains
D. had been rained
He is not a pilot, but he wishes he ____(be).
He ordered the work ____(start) at once.
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