[观察例句]
1．What seemed strange before now appears quite normal to Xie Lei.
2．It's important that Xie Lei keeps a balance between her studies and her social life.
3．That is why today over 40% of Californians speak Spanish as a first or second language.
4．Her tutor explained that she was supposed to read lots of information to help form a wise opinion of her own.
5．He made it quite clear that he preferred to study English.
6．The fact that she seemed to develop normally was very encouraging.
[归纳用法]
1．以上例句皆为主从复合句，句中用了相当于名词作用的从句(即名词性从句)在句中充当成分。
2．例句1为what引导的主语从句。例句2中it为形式主语，真正的主语为后面that引导的主语从句。
3．例句3为why引导的表语从句。
4．例句4为that引导的宾语从句。例句5中it为形式宾语，真正的宾语为后面that引导的宾语从句。
5．例句6为that引导的同位语从句。
名词性从句是在句子中起名词作用的句子。名词性从句的功能相当于名词词组，它在复合句中能担任主语、宾语、表语、同位语等，因此根据它在句中不同的语法功能，名词性从句又可分别称为主语从句、宾语从句、表语从句和同位语从句。
