一、主语从句
　　1. 主语从句必须有引导词，如果主语从句中从句表陈述，则一定用that引导。这里that无实际意义，类似于古代汉语中的“之”用来取消句子独立性。如：That he was late made me angry.
　　2. 当主语从句表示不确定的“是否”选择关系时，则只能用whether引导而不用if。如：
　　Whether he will go abroad is not decided yet！
　　3. 当主语从句表示疑问时，用相应的疑问句加陈述句加陈述语序的句式，此时绝不能再加that.如：When he will come here will be announced in 20 minutes.
　　二、宾语从句
　　1. 当主句谓语动词为think, suppose, expect, believe, imagine, guess等词时，如果宾语从句是否定含义，则否定前移。如：I don’t believe he is a thief. 而不能说成I believe he is not a thief.
　　2. 在含宾语从句的复合句中,如果就宾语从句中的成分提问、疑问句放在主句前（know做主句谓语动词时除外），主句变疑问语序，而宾语从句仍用陈述语序。如：
　　When do you think they should put their bikes
　　Do you know where they should put their bikes
　　3. whether 与if 的区别
　　（1） 引导让步状语时只用whether.如:Whether it rains or not, you must go to school.
　　（2）表语从句或同谓语从句中只能用whether
　　如：The problem whether he will be killed will be discussed.
　　（3） 与不定式或or not 连用时，应用whether引导。如：I don’t know whether to do it or not.
　　三、几组重要的连接成分
　　1. who/whoever, what/whatever的区别
　　一般说来，what/who 含特指意义，意为“什么/谁；而whatever/whoever含泛指意义，意为”无论什么/无论谁“。如：It is generally considered unwise to give a child _____ he or she wants.
　　A. however   B. whatever    C. whichever   D. whenever
　　2. where, when, why等连接副词引导的名词性从句。
　　where., when, why 等连接副词也可以引导名词性从句，使用的关键是：这个词必须符合句子的逻辑要求。如：
　　--I drove to Zhuhai for the air show last week
　　--Is that ______ you had a few days off
　　3.”介词＋who（m）”引导的宾语从句与”介词＋whom”引导的定语从句的区别。
　　介词后面的引导词用主格还是宾格，决定于它在宾语从句中作主语还是宾语。如：
　　It was a matter of _______ would take the position.
　　四、名词性从句中的插入成分
　　此时应注意两点：一是从句仍然不倒装，而在插入成分上倒装；二是要注意主语的主格和宾格的选择。如：
　　_____ you have seen both fighters, ______ will win
　　A. Since, do you think who B. As, who you think
　　C. When, whoever              D. Since, who do you think
　　五、引导词that的省略
　　引导宾语从句时，that可以省略，但引导主语、表语和同位语从句时,that不能省。
　　China’s success in manned-spacecraft travel shows ______ our country has become one of the greatest powers in space research.
　　A.what   B. which    C. /     D. it that
　　六、同位语从句引导词where、when的用法
　　说明先行词内容的同位语从句的引导词where、when与被说明的名词在概念上不一致。但引导定语从句的引导词却必须保持一致。试比较：
　　1.They arose the question______ we were to get so much money.
　　2.This is the house ________ the great man Mao Zedong was born 110 years ago.
　　A. where    B. that    C. about which    D. in which
　　1. I remember _____ the factory owned a small workshop and 2 machines.
　　A. when  B. how   C. whether  D. what
　　2. He always thinks of ______ he  can do more for the people.
　　A. what   B. how  C. if     D. whatever
　　3. What the doctors really doubt is _____ my mother will recover from the serious illness soon.
　　A. when  B. how   C. whether   D. why
　　4. Some college students are seen doing _____ work they can find to support themselves.
　　A. that    B. which   C. whatever   D. no matter what
　　5. After _____ seemed an endless effort, the patient was finally able to carry out _____seemed a perfectly normal walk.
　　A. what; what   B. that; that    C. it; that   D. which; like
　　答案：1. A   2. B  3. C   4. C  5. A