问题补充:
My friend’s flight had taken off I got to the airport to see him off.
A. while
B. after
C. before
D. until
答案:
A. while
B. after
(答案→)C. before
D. until
解析:
试题分析: 句意:在我到达机场送朋友前,他的航班已经起飞了。while当……的时候, after在……之后, before在……之前,until直到……。take off起飞,see off送行。got to一般过去时,had taken off过去完成时,可知主语动作发生在从句之前,故选C.