题目

The flowers his friend gave him will die unless ___ every day. A.watered                                                        B.watering C.water                                                           D.to water 答案：A 解析: unless后接省略形式。flowers和water之间是关系要用被动语态。同时unless从句的主语与主句的主语相同，常常省略其相同成分，故选A项，表示被动。动词-ing形式表示主动；不定式常用作目的状语。

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