一、主语从句
1．引导主语从句的连接词：从属连词that，whether/if连接代词what，who，whom，whose，whatever，whichever，whoever等；连接副词when，where，why，how，whenever等。
①That they were in truth sisters was clear from the facial similarity between them.从她们的面貌相似度就能清楚地看出她们真是亲姐妹。
②What struck me most in the movie was the father's deep love for his son.
影片中最打动我的是父亲对他儿子深深的爱。
2．主语从句一般放在句首，但有时也可用it作形式主语，而将主语从句移到句子的末尾。
常见的句型：
(1)It＋be＋形容词(necessary/likely/important/uncertain等)＋that从句
(2)It＋be＋名词(短语)(a pity/shame/no wonder/no surprise等)＋that从句
(3)It＋be＋过去分词(said/reported/decided/believed等)＋that从句
(4)It＋不及物动词(seem，appear，happen等)＋that从句
①It is uncertain what side effect the medicine will bring about，although about two thousand patients have taken it.
尽管大约两千名患者已经服用了这种药，但是它会带来什么样的副作用还不清楚。
