would do 和was to open when he ____ the door,he found his keys were nowhere.A.to,by B.

would do 和was to open when he ____ the door,he found his keys were nowhere.A.to,by B.
when he ____ the door,he found his keys were nowhere.A.to,by B.by,to C.had opened D.was to
.将要开的时候,但是would open 是will open的过去式,虽然常用作过去常常的意思,但是也是will do的过去式啊~也可以理解过过去要开门的时候啊,怎么A错了,错哪里了