运输市场的()是市场主体支配交换客体这一时间的长短。

A.成本结构

B.资金结构

C.使用结构

D.时间结构

It's quite a time _____ Liu Xiang was injured in the foot, but we're sure it won't be long _____ he returns to

the track. [ ]

A. after; when

B. before; since

C. that; when

D. since; before