在托福考試備考中，語法問題一直以來都是很多同學(xué)們比較頭疼的一個問題，并且托福閱讀、寫作以及口語等方面都對學(xué)生語法方面有著較高的要求。今天A加未來小編就為大家講解托福語法中有關(guān)主語從句的相關(guān)內(nèi)容，一起來了解一下吧！

　　1.主語從句常規(guī)會出現(xiàn)在句首，位于主句謂語之前：

　　Why and how these people spread out into central and southern Africa remains a mystery,but archaeologists believe that their iron weapons allowed them to conquer their hunting-gathering opponents,who still used stone implements.

　　2.主語從句在句首往往會顯得句子頭重腳輕，所以實(shí)際閱讀中我們會見到大量形式主語it代替主語從句位于句首的情況，為的是達(dá)到句子結(jié)構(gòu)的平衡：

　　To compare the compositions of a meteorite and the Sun,it is necessary that we use ratios of elements rather than simply the abundances of atoms.

　　It was no accident that many leading Roman soldiers and statesmen were writers of high caliber.

　　Soon it was realized that this principle of faunal(animal)succession was valid not only in England or France but virtually everywhere.

　　由以上的句子我們可以總結(jié)出三個常見的句式分別是：

　　It is+adj.+主語從句

　　It is+n.+主語從句

　　It is+done.+主語從句

　　注意前兩種句式中的be動詞本質(zhì)上是系動詞，所以也可被換成其他系動詞，例如：

　　Contrary to the arguments of some that much of the pacific was settled by Polynesians accidentally marooned after being lost and adrift,it seems reasonable that this feat was accomplished by deliberate colonization expeditions that set out fully stocked with food and domesticated plants and animals.

　　But as more and more accumulations of strata were cataloged in more and more places,it became clear that the sequences of rocks sometimes differed from region to region and that no rock type was ever going to become a reliable time marker throughout the world.

　　另外需要注意的是，形式主語it結(jié)構(gòu)后邊所跟的主語從句個數(shù)不限，可以是一個或過個并列，從以上例句就能看到這一點(diǎn)。

　　好了，以上就是A加小編關(guān)于托福語法中有關(guān)主語從句的內(nèi)容指導(dǎo)，希望能夠幫助大家更好的熟悉這部分語法內(nèi)容。更多托福考試問題，歡迎隨時咨詢我們！

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