that 用作代詞
1.that 用作指示代詞（復(fù)數(shù)形式是those）,其指代意義同形容詞用法,同時它還可以用作定語從句中的先行詞；還可為了避免重復(fù),代替前述名詞.
That is what he told me.
What is that (which) you have got in your hand?
The price of rice is higher than that of flour.
2.that 用作關(guān)系代詞,引導限制性定語從句.先行詞可人可物,用法相當于who或which.（但是在下列情況下多用that：先行詞既有人又有物時；先行詞有形容詞最高級、序數(shù)詞、不定代詞、very,only等修飾時；先行詞是不定代詞時）
He talked about the teachers and schools that he had visited.
I think it one of the most wonderful films that the film company has ever produced.
She has little information that is useful for our research.
Is there anything that I can do for you?
請注意,that 在定語從句中作賓語時通?？墒÷?
The books (that) I sent you will help you in your studies.