When he the door he found his keys were nowhere．A. would open B. opened C. had opened D.

问题补充：

When he the door, he found his keys were nowhere．

A. would open

B. opened

C. had opened

D. was to open

答案：

A. would open

B. opened

C. had opened

D. was to open

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。