题目

When he  _______ the door, he found his keys were nowhere.                         A. would open           B. opened                 C. had opened           D. was to open 答案：D 解析: 考查非谓语动词。动词不定时的用法。句意为：当他要打开门的时候,他发现他的钥匙不见了。动词不定时表示将要发生的动作。

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