问题
选择题
He was about to leave the office for home _______someone knocked the door and asked for some help.
A．until
B．while
C．as
D．when
答案
答案：D
题目分析:句意：他正要离开办公室回家这时有人敲门求助。固定句型：be about to do …..when 正要做某事……这时，选D。
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