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This robot is supposed to save a lot of labor, but it remains a problem if it .

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This robot is supposed to save a lot of labor, but it remains a problem if it .

This robot is supposed to save a lot of labor, but it remains a problem if it ______.

   A. is B. saves C. does D. has

试题答案

C

解析:

do(es) 是代动词,用来代替上文save a lot of labor。