一．代词的指代
1．that的指代作用
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 of speaker with that of listener, and it calls for occasional “digestive pauses” by both.这里that指代前面的the role。
No bread eaten by men is so sweet as that earned by his own labor.
2．one的指代作用
one指代带不定冠词的单数可数名词，复数为ones。the one指代带定冠词的单数可数名词。如：
A good writer is who can express the commonplace in an uncommon way.
[A] that [B]he [C]one [D]this
答案为[C]
3．do的替代作用。
do代替动词，注意数和时态的变化。如：
For him to be re-elected, what is essential is not that his policy works , but that the public believe that it does.