【分析】最佳答案是D。it 用以指身份不明的人。若指身份明确的人，则不宜用it。比较：
(1) Mr Smith is at the door. _______ wants to see you.
(2) Someone is at the door. ________ must be Mr Smith.
A. He B. It
C. This D. That
第(1)题选A，因为来者身份明确;第(2)选B，因为来者身份不明确。
4. "Excuse me, I want to have my watch fixed, but I can't find a repair shop." "I know ________ nearby. Come on, I'll show you."
A. one B. it
C. some D. that
【陷阱】容易误选B。
【分析】最佳答案是A。it 和 one 的区别可简单地概括为：it = the + 名词，one = a + 名词。如：
I haven't got any pens, and I want to borrow one. 我没有钢笔，我想借一支。(one = a pen)
I have two pens, and I can lend one to you. 我有两本支钢笔，我可以借一支。(one = a pen)
I have a pen, and I can lend it to you. 我有一本钢笔，我可以把它借给你。(it = the pen)
在上面一题中，one 相当于 one 相当于 a repair shop。请做下面一题(答案选A)：
There is only one English-Chinese dictionary in that book-shop. I wonder if you still want to buy _______.
A. it B. one
C. another D. any
5. Will you see to _______ that my children are taken good care of while I am away?
A. it B. me
C. yourself D. them
【陷阱】几个干扰项均有可能误选。
【分析】最佳答案是A。it 为形式宾语，真正的宾语是空格后that引导的宾语从句。see to 意为“负责”、“注意”，其中的 to 为介词，不宜直接跟that引导的宾语从句，遇此情况可借助代词 it。请做下面两题，答案也是选 it：
(1) I'll see to _______ that all these letters will be sent to the post before twelve.
A. it B. me
C. which D. them
(2) Will you see to _______ that the luggage is brought back as soon as possible?
A. me B. yourself
C. it D. them
类似以上 see to 用法的短语还有 depend on, answer for 等。如下面两题答案也选 it：
(1) You may depend on _______ that he will turn up in time.
A. it B. me
C. which D. them
(2) I can't answer for ________ that the boy is honest.
A. it B. me
C. which D. them
