◎ 题干
E-shopping, when properly _____, can save us a lot of time and money.

[     ]

A. doing
B. to do
C. having done
D. done
◎ 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“E-shopping, when properly _____, can save us a lot of time and money. [ ]A. doing B. to do C. having done D. done …”主要考查了你对  【过去分词】  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。