关于逗号的问题，都出现在选择题当中，常常会给我们设置陷阱。我们具体来看一下。
1._________ is reported, the project was completed yesterday.
A. It B. As C. This D. What
【分析】许多同学会忽略了句子中间的逗号而认为此题是主语从句，于是将答案误选为A。把It当作句子的形式主语，况且It is reported 也是一个常用句型，读起来也很有英语语感。而事实上，答案选错了，因为在主语从句中的连接词that不能省略。正确答案应该选B，构成一个非限制性定语从句。
2. The purpose of new technologies is to make life easier, __________________ it more difficult.
A. not make B. not to make C. not making D. do not make
【分析】许多同学会一看到句子中的逗号就会想到此题是考查非谓语动词表结果的用法：现在分词表结果时，跟句子间可用逗号隔开;而不定式表结果时，与句子间常不用逗号。于是将答案误选为 C。其实，在此句中，逗号相当于连词and 或 but, not to make it more difficult是与逗号前面不定式 to make it easier相并列，对之进行补充或说明，因此答案应该选B。全句的意思是：新技术的目的是为了使生活变得更容易，并不是使生活变得更困难。两个不定式在句子中作表语说明主语的内容。有如此用法的词还有 idea, suggestion, hope, goal, aim, dream 等，如：
3.(1) My idea is to visit the museum, _________ to the park.
A. not go B. not going C. not to go D. do not go
(2) My dream is not to live on the earth but __________________ on the moon.
A. live B. living C. to live D. being living
同学们不难看出，以上两题的答案都是C。但值得一提的是：不定式并列作表语时，若否定的不定式在前而肯定的不定式在后，一般须用but连接，而不用逗号。
4.(1) If he is only interested in your books, _________ just shows how shallow he is.
A. as B. which C. what D. that
(2) If you want to go, _________ is quite all right with me. (from www.nmet168.com)
A. that B. which C. and it D. so
(3) When I say two hours, __________________ includes time for eating.
A. as B. which C. what D. that
(4) If you want a double room, _________ will cost another $ 15.
A. as B. which C. what D. that
(5) If you have the money, _________ will be OK.
A. that B. which C. and it D. so
(6) Unless I’m very much mistaken, _________ is my watch you are wearing.
A. as B. which C. what D. that
它们的答案也应该选 that，而不应该选 which。 (from www.nmet168.com)
5. There were a lot of people in the reading-room, most of _________ with their heads bent down over their books.
A. them B. whom C. that D. which
【分析】许多同学会根据句子中的逗号，想当然地认为这是考查非限制性定语从句，从而将答案误选为 B。但事实上，逗号后面由于没有谓语动词，根本不是完整的句子，而是一个“代词。
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