The candidate was about to get in the car _ suddenly a man with a mask appeared and shot at him.
A. while
B. after
C. as
D. when
网友回答
A. while
B. after
C. as
(答案→)D. when
解析：考查固定句型。be about to do sth when…正要做某事…在这时…句意：那位候选人正要上车，在这时突然有个带着面具的男的出现并且朝他射击。