GRE閲讀主題句應該如何理解

1. 判斷句;

2. 概括文章將來結構。

比如一個句子：Your minds changed my attitude. 這句話中並沒有情態動詞和系動詞，因此這句話自然不是判斷句，也就不是主題句。但只要在這句話中加入一個正負褒貶詞，即一個詞表明作者的'態度或觀點的詞即是判斷句了。比如，Your minds successfully changed my attitude即是判斷句了。

另外，如果一個句子不是判斷句，只要它能夠概括文章將來結構，及文章後面會從哪幾個方面來説明，也是主題句。比如，People are living longer now. 這句話一定不是主題句，而如果這句話是，People are living longer now since the improvement of food condition and the development of medical technology.這句話即是主題句了。因為它概括了文章後面會從哪幾個方向來進行説明。

如果考生在新GRE閲讀題中掌握好了主題句判斷方法，很多文章便可以很快把握文章的結構框架，幫助後面文章的理解。

比如一篇文章的開頭是，Mycorrhizal fungi infect more plants than do any other fungi and are necessary for many plants to thrive， but they have escaped widespread investigation until recently for two reasons. First， the symbiotic association is so well-balanced that the roots of host plants show no damage even when densely infected. Second， the fungi cannot as yet be cultivated in the absence of a living root.