问题
选择题
.
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
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。