I get on the bus when I heard someone calling me from behind.A. was toB. was going toC. wo

问题补充：

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

答案：

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。