Question

—Have you seen your friend off ?
—Yes. I watched the train leaving the station        it disappeared from sight.

A．unless

B．as if

C．so that

D．until

Answer 1

D

试题分析：考查词和词组意思，unless意思“除非”， as if意思“好像”，so that意思“以至于”，until意思“直到……”，句子意思“我看卓火车离开车站直到从我的眼前消失”，所以选D
点评：固定词组see off意思“送行”，watch sb do sth意思“看到某人做什么”，watch sb doing sth意思“看到某人正在做某事”，强调动作正在发生。