I got on the bus he got off.A. AsB. WhileC. UntilD. Till

问题补充：

I got on the bus, he got off.

A. As

B. While

C. Until

D. Till

答案：

(答案→)A. As

B. While

C. Until

D. Till

解析：句意：当我上车时，他下车了。As用作连词，意为“当……的时候”，故选A。While用作连词表示对比，后面跟延续性动词；故选A。