Is______necessary to change trains at Beijing?A.thisB.thatC.itD.he
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C解析不定式、动名词作主语时常用形式主语it来代替，而把真正的主语──不定式和动名词后置。常住it作形式主语的动名词结构有：It’s no use (no good, no point) doing sth. It’s a waste of time doing sth.等。故本题选C。又如：It was no good quarrelling again