摘要： into use in April.2000.the hotline was meant for residents reporting water and heating supply breakdowns. A.Put B.Putting C.Having put D.Being put 答案 A 解析 考查过去分词作状语.句子的主语是the hotline与“投入使用 存在着被动关系.而且表示过去的事情.所以排除D项.

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