When Steven suddenly remembered that he had left his mobile in the office the train was a

问题补充：

When Steven suddenly remembered that he had left his mobile in the office, the train was already .

A. on the go

B. on the rise

C. on the run

D. on the move

答案：

A. on the go

B. on the rise

C. on the run

(答案→)D. on the move

解析：考查介词短语。A忙碌；B上涨；C在逃，奔波；D在移动中。句意：当史蒂夫突然想起来他的手机落在办公室的时候，火车已经开动了。故选D。