名词性从句在句子中起名词作用的句子叫名词性从句.1宾语从句；2主语从句；3表语从句；4同位语从句主语从句在另外一个句子中做主语的句子叫主语从句。Howthebookwillselldependsonitsauthor.Thatheisthebeststudentintheclassisobvious主语从句常用it 作形式主语放句首因而我们常见到这种句式：It+be+n./adj/-ed从句（that,whether,etc.)例：Itsapitythatyoushouldhavetoleave.=Thatyoushouldhavetoleaveisapity.ItisgreatthatIhaveateacherlikeyou.=ThatIhaveateacherlikeyouisgreat.主语从句的连接词一、主语从句1.连词that(无词义, 不作成分, 不能省略);whether(是否),if不能位于句首。2.That he will come and help us is certain.3.Whether we will succeed is still a question
