一。有无标点符号会影响对句意的整体理解。如：

　　The students who knew about the floods took another road. 知道道路被淹没的那些学生改道走了。（言外之意：只有那些知道道路被淹的学生才改道走了，不知道的学生仍然走被淹的道路。）

　　The students， who knew about the floods， took another road. 同学们知道道路被淹都改道走了。（言外之意：同学们都知道道路被淹，都改道走了。）

　　I have just remembered something she said.

　　我刚刚想起她说过的一件事。

　　“I have just remember something，” she said.

　　她说：“我刚想起一件事。”

　　二。标点符号的位置会影响句意。例如：

　　The policeman said， “The bus driver was to blame for the accident.”

　　警察说：“那位公共汽车司机对这次事故负责。”

　　“The policeman，” said the bus driver， “was to blame for the accident.”

　　那位公共汽车司机说：“那个警察应对这次事故负责。”

　　三。标点符号会影响答案的选择。例如：

　　Li Ping said nothing ______ made her mother sad the day before yesterday.

　　A. it B. that C. which

　　Li Ping said nothing， ______ made her mother sad the day before yesterday.

　　A. it B. that C. which

　　解析： 前一句选 B 项，这是限制性定语从句，先行词是 nothing ，用 that ，意为“前天李平没有说使她母亲伤心的话。”后一句选 C 项，用了逗号，变成非限制性定语从句，用 which ，意为“前天李平什么都没有说，这使她母亲很伤心。”

　　I have two brothers， ______ are middle school students.

　　A. both of whom B. both of them

　　C. of them both D. whom

　　I have two brothers. ______ are middle school students.

　　A. Both of whom B. Both of them

　　C. Of them both D. Whom

　　解析： 前一句用了逗号，说明“ … are middle school students ”是个非限制性定语从句，应选用关系代词，故正确答案为 A 项。后一句中用了句号，说明前后两句在语法结构上是完整的两个句子，故正确答案选 B 项。

　　______ no buses， we had no choice but to walk home.

　　A. There had B. There being

　　C. It being D. There were

　　______ no buses. We had no choice but to walk home.

　　A. There had B. There being

　　C. It being D. There were

　　解析： 前一句中用了逗号，表示前一部分不是一个单独的句子。因为逗号通常不能连接两个独立的句子，正确选项为 B 项，构成独立主格结构。后一句中用了句号，表示前后两部分是两个完整的句子，又因为在表示存在句的 there 后不能用 have ，故正确答案为 D 项。