Do you know if /whether Cathy goes to school early? 注意:只能用whether而不用if的三种情况如下: ①与or not连用:They asked us whether or not we were coming. ②在介词之后:It depends on whether it is going to rain. 3.在不定式之前:We haven’t decided whe...
when是必然发生(will happen);if是可能发生(might happen) 例句: I'll take care of it when I am free this afternoon. (今天下午我有时间,我会处理。)→一定有时间 I'll take care of...
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