—How long do you think it will be we win the football World Cup?—Perhaps twenty years.A.

问题补充：

—How long do you think it will be we win the football World Cup?

—Perhaps twenty years.

A. when

B. since

C. that

D. before

答案：

A. when

B. since

C. that

(答案→)D. before

解析：句型考查题。It will be +段时间 +before …。句意：你认为要过多久我们才能赢得足球世界杯？也许二十年。