.Mary quickly closed the door of her room her father could reach it to keep him out.A. be

问题补充：

.

Mary quickly closed the door of her room her father could reach it to keep him out.

A. before

B. when

C. as

D. while

答案：

(答案→)A. before

B. when

C. as

D. while

解析：连词辨析。Before在……之前； when当……时；as随着，由于；while然而，当……时。句意：，为了把他挡在外面，在他能够到它之前玛丽快速的把她房间的门关上了。故选A。