非限制定语从句中,先行词可以为,什么?可以用那些关系词来引导,怎么看在...答:I study at college and my sister (studies) at high school. 我读大学,我妹妹读高中。 二、在when, while, if, as if, though, until, once, whether, unless等连接的状语从句中, 常省略跟主句相同的主语和be动词。 When (I am) in trouble I always turn to her for help. 当我有困难时总...