⑥ It
不定式做主语，通常用it作形式主语
that从句做主语，通常用it作形式主语
不定式或that从句做宾语，用it作形式宾语
She made it possible for us to attend the movie.
She made possible our attendance at the movie.
She made our attendance at the movie possible.都对
⑦ 避免代词指代不清的问题
有时最好的办法去解决代词问题的是删除代词。在长句子的时候，代词像 it或者them 不可避免的会产生指代不清的问题。这个时候要么重复先行词，要么找一个相似的同义词替代。
1) After roasting the deer, the hunter extinguished the fire and then searched for a tree to hang it from.. 这里的it 在语义上指代 deer但是在语法也可能会造成指代fire的问题
2) After roasting the deer, the hunter extinguished the fire and then searched for a tree to hang
60
the deer from
3) After roasting the deer, the hunter extinguished the fire and then searched for a tree to hang the meat from (meat 指代 deer)
代词：
12th Edition:101, 113, 124, 132， 1, 7, 23, 47, 91, D42
Verbal Review:71, 72, 74, 85,102, 107，12, 15, 19,29,41,44,49, 53,65,67
2nd Edition:50,68, 70, 80, 98, 105
6. 回家作业
1)Less than 35 years after the release of African honeybees outside Sao Paulo, Brazil, their descendants, popularly known as killer bees, had migrated as far north as southern Texas.
(A) Less than 35 years after the release of African honeybees outside Sao Paulo, Brazil,
(B) In less than 35 years since releasing African honeybees outside Sao Paulo, Brazil,
(C) In less than the 35 years since African honeybees had been released outside Sao Paulo, Brazil,
(D) It took less than 35 years from the release of African honeybees outside Sao Paulo, Brazil, when
(E) It took less than the 35 years after the time that African honeybees were released outside Sao Paulo, Brazil, and then
1) 分词短语在句首起状语作用,逻辑主语等于句子主语
2) it不能指代介词短语, it可以指代主语从句和不定式结构: It is difficult to do this research. It is important that we finish on time. 在这两个例子中it分别指代to do this research和that从句
3) 现在完成时的时间状语 for, since, so far, ever, never, just, yet, till / until, up to now, in past years…
(A)正确, after + n.结构避免了逻辑主语问题; less than 35 years after …符合习惯用法
(B) since releasing放在句首,逻辑主语等于句子的主语their descendants, 不符合逻辑; since是现在完成时的标志和had migrated矛盾; since的使用不符合习惯用法
(C) since是现在完成时的标志和had migrated矛盾; since的使用不符合习惯用法
(D) it不能指代介词短语from the release…
(E) it不能指代介词短语from the release…
2. Japanese researchers are producing a series of robots that can identify human facial expressions, to which they will then respond; their goal is primarily creating a robot that will empathize with us.
(A) expressions, to which they will then respond; their goal is primarily creating
(B) expressions, then responding to them; primarily to create
(C) expressions and then respond to them; the researchers' primary goal is to create
(D) expressions as well as giving a response to them; their primary goal is creation of
(E) expressions and responding to them; primarily, the researchers' goal is creating
1)指代歧异; 一般来说避免指代歧异的方法有三个: (参考白勇语法)
a)重复代词指代的对象
b)用 such + n.或者指示代词 this/these/those + n.代替代词
