看你把that放在什么地方.
1.作指示代詞,同this用法.
This/That is an apple.
2.作形容詞,同this用法.
I prefer that/this one.
3.做連詞,引導(dǎo)從句時(shí),同which（指物）
I will buy the red one that/which my wife likes very much.
4.做連詞,在強(qiáng)調(diào)句中,同who（指人的時(shí)候）
It was me that/who locked the door.
5.作副詞表示程度時(shí),近so:
I like it so much.
I really care about you that much.
6.作形式主語(yǔ),近it：
That was my pen.
It was my pen.
以上種種,有的是用法一致,意義有別.有的可以互換,也有特殊情況不能互換的.這里不多說(shuō)了.