When he ______ the door, he found his keys were nowhere．
A．would open B．opened C．had opened D．was to open
When he ______ the door, he found his keys were nowhere．
A．would open B．opened C．had opened D．was to open
D
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。