托福写作常用名词性从句一：主语从句
常见的主语从句形式莫过于以that从句为主语、it为形式主语的倒装结构，进一步又可细分为以下两种：
1. It is + adj. + that...
这种结构常翻译为“……的是”，用于强调表达某种客观事实。
It is undeniable that opportunities and choices could sometimes make all the difference in a person's life.
不可否认的是，有时在一个人的人生中，机遇和选择能够扭转乾坤。
It is unanvoidable that the rapid progress of industry leads to severe pollution.
工业的迅速发展不可避免的导致严重污染。
It is unquestionable that schooling plays an essential role in children's personal development.
毋庸置疑，学校教育在孩子们的个人发展中起到了至关重要的作用。
2. It is + v.-ed + that...
这种结构常翻译为“人们/有人……”，用于表达某种有代表性的主观观点。
It is assumed that education should start as early as possible.
有人设想，教育应当尽可能早地开始。
It is generally held that robots are more effecient than human labors.
众所周知的是，机器人比人工更有效率。
It is reported that the temperature will decline sharply in one or two days.
据报道，近日气温将明显下降。
托福写作常用名词性从句二：宾语从句
Some people claim that government should be mainly responsible for the environmental pollution.
一些人声称，政府应当为环境污染负主要责任。
Many experts point out that it is the inevitable result of the development of modern society.
许多指出，这是现代社会发展不可避免的结果。
显然，宾语从句的用法相对较为单一，主要用于表达主观观点，包括作者本人观点或引用他人观点为己所用。
托福写作常用名词性从句三：同位语从句
该句型利用that从句来解释说明先行词所代表的具体内容，在写作中的用法主要分为以下两类：
1. 表主观观点（the view/point/opinion/notion/assumption/conception that...）
The assumption that computers will sooner or later replace teachers cannot hold water.
电脑迟早会教师的设想站不住脚。
2. 表客观事物（the fact/problem/phenomenon/practice that...）
The fact that young people nowadays are self-centered is largely the parents' fault.
当今年轻人自我中心的事实，主要是父母的责任。
此外，同位语从句还能很好地解决“句子做主语”的语法问题，如：
The government subsidizes the space exploration is beneficial to the development of human being in a long run.
该句的主语看似The government subsidizes the space exploration，但作为一个拥有独立完整的主谓宾结构的句子，这个结构显然不能充当主语。事实上，这是笔者在教学中发现的学员常犯的语法错误之一，即不清楚应当用哪些结构来充当句子的主语。此句可改为：
The practice that the government subsidizes the space exploration is beneficial to the development of human being in a long run.
政府补贴太空探索的做法对人类的长远发展是有益的。
经此修改，原句主语变为一个以practice为先行词的同位语从句（The practice that the government subsidizes the space exploration），问题迎刃而解。
