that of的用法：(1)that of代替了前面的某个内容；(2)that of指代“那一类”。(that of = the size of)。
that of的用法
(1)that of代替了前面的某个内容
The size of China is bigger than that of USA.(that of = the size of)
(2)that of指代“那一类”
His manner was that of someone accustomed to mixing with nobles.
(他的言行举止属于那种习惯于跟贵族打交道的人。)
(3)that用于强调上文提到过的词或短语表达的同类意思，thatof…的意思是“…的同类的那种东西/事情”。
thatof不能省略,否则后面的名词短语，就成了前面名词短语的同位语,也就是说前者是后者的具体解释,二者是同一种东西的不同说法.但是原文指的是前者是一种东西,而后者是与前者同类的另一种东西。
例句
The effect was that of two guitars playing.
这样的效果是两架吉他在演奏。
Her novel was by far better than that of any other writer sin the city.
她的小说比那个城市的其他作家写的书好得多。
I said with a laugh that of course he had now found his man.
我笑着说这么说来现在他已经找到了他要找的人。
