单项选择题

风化煤与原煤相比有( )特点。

A.风化后的煤强度略有加强
B.风化后
C.H含量上升C风化后虽然黏结性降低，但焦油产率不变
D.风化后的煤发热量降低
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单项选择题
一台机器空运转，对外不作功，这时机器的效率()。
A.大于零
B.小于零
C.等于零
D.大小不一定
多项选择题
Should is used for pseudo subjunctive in the following sentences. ( ) A. The doctor ordered that she stay in bed for another week. B. It is necessary that he be sent there at once. C. He said that the thief should be punished. D. The president insists that the prime minister should attend the meeting.
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