如：Each cigarette a personsmokes does some harm, and eventually he may get a serious disease from itseffect.
It was during the 1920’sthat the friendship between the two American writers Hemingway and Fitzgeraldreached its highest point.
that指代不可数名词和单数可数名词(如是复数，用those)，后面通常跟有修饰语，如出现在比较结构中的that of。如：Conversation calls for a willingness to alternate the role ofspeaker with that of listener, and it calls for occasional “digestive pauses”by both.
No bread eaten by man is so sweet as that earned by his own labor.
one指代不确指的单数可数名词，复数为ones。the one 指代确指的单数可数名词。如：
A good writer is one who can express the commonplace in anuncommon way.