◎ 题干
_____ we call a machine is really a kind of tool that can do  work for man.        

A. When                                
B. That      
C. What                              
D. Which
◎ 答案
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◎ 解析
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◎ 知识点
    根据n多题专家分析,试题“_____we call a machine is really a kind of tool that can do work for man.[ ]A. WhenB. That C. WhatD. Which…”主要考查了你对  【连接代词】【主语从句】  等知识点的理解和应用能力。关于这些知识点的“档案”,你可以点击相应的链接进行查看和学习。