It常作形式主语,代替主语从句放在句首,但是具体替代由哪个连词引导的从句,需要根据实际情况来判断和选择应用,不都是由that引导.例如:
It is doubtful whether they can solve the problem by themselves.
It常作形式主语,代替主语从句放在句首,但是具体替代由哪个连词引导的从句,需要根据实际情况来判断和选择应用,不都是由that引导.例如:
It is doubtful whether they can solve the problem by themselves.