雅思英语:名词性从句讲解
主语从句：主语从句在复合句中充当主语，大多数主语从句都可以用it代替，作形式主语把主语从句置于句尾。that引导的主语从句可用it代替，that不可省。
That education is important is clear.(that不可省)It is clear that education is important.(that不可省)
很明显，教育是很重要的。
That a round-trip to Mars would take more than a year is estimated.
It is estimated that a round-trip to Mars would take more than a year.
据估计，飞到火星来回的时间要超过一年。
Whether we should develop nuclear power plants is still doubtful.
It is still doubtful whether we should develop nuclear power plants.
是否应当发展核电厂仍然值得怀疑。
宾语从句：宾语从句在复合句中充当宾语，雅思写作中很常用，一般用来提出观点。
Some people hold that the development of tourism produces some adverseimpacts on traditional culture.
有些人认为发展旅游业会对传统文化产生负面影响。
Experts predict that tele-education will play an even more significant role inthe prospective future.
专家预言远程教育将会在不久的将来起到更为重要的作用。
表语从句：表语从句放在连系动词后，充当复合句中的表语，一般结构是:“主语+连系动词+表语从句”。可以接表语从句的连系动词有be, look, remain, seem等。
雅思写作中表语从句两个常用句型请记好练熟:“The reason why… is that…”(注意这里的that不能换作because)，“It( this/that) is because …”
The reason why the environment is deteriorating constantly is that nowadayspeople still lack the awareness of environmental protection.(定语从句+表语从句双管齐下，体现句式多样性!)
环境不断恶化的原因是现如今人们仍然缺乏环保意识。
The most practical countermeasure is that more rigid laws and regulationsshould be laid down to penalize the violators.
实际的对策是制定更严厉的法律法规来惩处违规者。
One of the potential problems is that constant job transition can not securethem a stable and bright job prospect.
一个潜在的问题是频繁的跳槽不能够确保他们有一个稳定辉煌的职业前景。
同位语从句：同位语从句在复合句中充当同位语，对其前面的名词作进一步解释，说明名词的具体内容。雅思写作中常用的能接同位语从句的名词有:belief, fact, hope, doubt, idea,news, conclusion, problem, likelihood。同位语从句一般由that引导，但也可以用关系代词(what, which, who)，关系副词(when, where, why, how)或whether / if引导。
There is some doubt (as to) whether we should perform animal experimentation.
对于我们是否应当进行动物实验仍然存在怀疑。
Einstein came to the conclusion that the maximum speed possible in theuniverse is that of light.
爱因斯坦得出的结论是，宇宙中速度是光速。
What we should do, when we should do, how we should do-these questionspuzzled us all day long.(作同位语的句子放在句首，后面要用破折号)
该做什么，什么时候做，怎样做—这些问题整天困扰着我们。
