1》如何识别主语从句
(1).见到引导词放在句首，并且没有被逗号隔开，
(2)it 。。。that...
2》如何识别宾语从句——只要实义动词后面有引导词就暂定为宾语从句，也可能是状语从句
宾语前面是实义动词，宾语是谓语的承受者
所以实义动词后可能是宾语，也可能是状语
She said (that) she would marry an old rich man.(宾语从句that可省略)
I wonder if(是否) I can pass the National Postgraduate Entrance Examination smoothly.
if== 翻译成如果就不是宾语从句，
if 只能做宾语从句的引导词，翻译成是否，而weather 能做所有名词性从句引导词
eg： This alone deonstrates that the televison business is not an easy world to survive in. A fact underlined by statistics shows that out of eighty European televison networks no less than 50% took a loss in 1989.