I was about to get on the bus someone called.A. asB. whenC. beforeD. while

问题补充：

I was about to get on the bus someone called.

A. as

B. when

C. before

D. while

答案：

A. as

(答案→)B. when

C. before

D. while

解析：考查固定句型。固定句型：be about to do sth when….正要做某事在这时…；when是并列连词，在那时；后面的句子表示意料之外的结果。句意：我正要上车，在这时有人叫我。