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
网友回答
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。