问题补充:
Some of the students are nearsightedthey spend too much time watching TV or playing online games.
A. when
B. though
C. because
D. unless
答案:
A. when
B. though
(答案→)C. because
D. unless
解析:句意:一些学生近视眼,因为他们花费太多的时间在看电视和网络游戏上。A当连接时间状语从句B虽然,转折连词,D如果不,条件状语从句。故选C,因为,连接原因状语从句。