The old man often advised the young workers on the machine and they learned quic
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The old man often advised the young workers on ________ the machine and they learned quickly．
A.to operate
B.how operate
C.how operating
D.how to operate
试题答案
D
解析：题意是“这位老工人就如何操作机器向年轻工人提出了建议，他们学得很快”。本题主要考查advise sb．+on+疑问词+不定式的用法，故选D项。其他均不符合结构。