四、注意that which的用法
that which中的which为关系代词，用以引导定语从句，其意为“……的事或物”，这是一种比较正式的用法，它通常可以用what代之。如：
That which (=What) many people say is not always true. 很多人说的话并不表示一定是真的。
That which (=What) I say and do is my own affair. 我说什么做什么是我自己的事。
They say the only real knowledge is that which can be measured. 据说唯一真实的知识是可以检验的知识。
The picture tries to convey an attitude towards life.
It happens in life that...
Such a situation seems fairly common in our society

五、注意that的替代词用法
指示代词that有时可用作替代词，用来代表前已提过的事物，以避免重复，如：
A grandparent's job is easier than that of a parent. 祖父母的任务比父母的任务要轻松一些。
A dog's intelligence is much greater than that of a cat. 狗的智慧比猫的高得多。
The dialect in one town may he quite different from that of the next town. 一个城镇的方言可能与另一个城镇很不相同。
The weather of Beijing is just as cold as that of Lanzhou, but colder than that of Shanghai. 北京的气候和兰州一样冷，但比上海冷。

六、注意that, this用作副词
指示代词有时可用作副词，其用法与so相似。如：
It isn't all that cold. 还没冷到那种程度。
It's about this high. 约摸这样高。
Is it this hot every day? 每天都这样热吗?
I didn't think it would be this easy. 我没想到会这样容易。
I didn't realize she was that ill. 我没想到她病得那么重。
The book is about this thick. 那本书大约有这么厚。
When you pay that much for a meal you expect the best. 一顿饭花那么多钱是想吃到最好的东西。