I get on the bus when I heard someone calling me from behind.
A. was to
B. was going to
C. would
D. was about to
网友回答
A. was to
B. was going to
C. would
(答案→)D. was about to
解析：考察固定句式。固定句式be about to do sth when…正要做某事在这时…该句式不能和将来时的时间状语连用。句意：我正要上车，在这时我听见有人从背后喊我。故D正确。