第1个回答 2014-05-09
it 可以用来指代时间、距离、人物，可以代替不定式、动名词（作形式主语）
也可以用来指代前文提到过的某一事物；
eg it is seven o'clock now.(时间)
it is 400 miles from A to B(距离)
do you really like it(前文提到的事物)
who is it？（是谁啊）
it takes me 3 hours to finish the work.(形式主语)
that用来指代过去的或远处的某一事物，也可用啦指代同类不同物，还可以引导定语从句。
eg the weather in China is much better than that in Japan.
which girl do you like better, this one or that one?