问题补充:
How long do you think it will be China sends another manned spaceship to the moon?
A. when
B. until
C. that
D. before
答案:
A. when
B. until
C. that
(答案→)D. before
解析:句意:你认为还要有多久中国才能发射另一个载人飞船上月球。这里do you think 是插入语,这句话用了固定句型:It will be+一段时间+before…,要多久才…,since也可以和一段时间连用,但是是:It is/has been+一段时间+since,所以选D。