问题补充:
How can they learn anything they spend all their spare time watching television?
A. when
B. though
C. while
D. before
答案:
(答案→)A. when
B. though
C. while
D. before
解析:考察连词辨析。A当…时;既然;B尽管,即使;C当…时;然而;D在…之前;句意:既然他们已经把所有的空闲时间都花在了看电视上,他们又怎么能够学到知识呢?根据句意本句中的when表示“既然”;故A正确。