状语从句在从句中充当状语成分，也就是在文章排除主谓宾的情况下所存在的成分。状语在一个句子里的作用有时间、目的、地点、原因、结果、让步、条件、方式等，所以状语从句就是表示上述作用的从句。在雅思写作中容易拿分的四大状语从句是什么？怎么用？

　　一、原因状语从句

　　能引导原因状语从句的词汇有：because，as，since，in that

　　例如：

　　World food output per head has risen by 4 per cent between the 1970s and 1980smainly as a result of increases in yields from land already in cultivation but also because more land has been brought under plough.

　　在20世纪70以及80年代，平均每人的食物产量增加了4%，主要是因为现有的耕地食物产量增加，还有一个原因是越来越多的土地被用来耕地。

　　The removal of subsidies stopped land-clearing and over-stocking, because they in the past had been the principal causes of soil erosion.

　　因为津贴的废除，导致开荒毁林以及过度放牧的停止，曾经这是水土流失的主要原因。

　　Such fuel crops are less likely to contribute to the greenhouse effect as they produce far less carbon dioxide, and absorb carbon dioxide as they grow.

　　这样的燃料作物相比之下更不太可能导致温室效应，因为燃烧他们产生的二氧化碳更少并且在这些作物的成长过程中会吸收二氧化碳。

　　介词词组有：because of, due to, as a result of, thanks to, owing to

　　二、结果状语从句

　　能引导结果状语从句的词汇有：so...that...

　　These remarkable beetles have evolved and adapted so successfully to the local environment that they have reached their natural boundaries.

　　这些甲壳虫进化以及适应当地的环境如此之快以至于他们的数量已经到达了自然界能到达的最大值。

　　The tuition fee increases so rapidly that many students take part-time jobs to lighten the financial burden of their parents.

　　教育费用增加如此之快以至于很多的学生参加兼职去减少父母的经济负担。

　　以上两个句子是最基本的句型，写作中可以采用这个基本句型的升级版，将之改为倒装句：

　　So successfully have these remarkable beetles evolved and adapted to the local environment that they have reached their natural boundaries.

　　So rapidly does the tuition fee increase that many students take part-time jobs to lighten the financial burden of their families.

　　将so提前，that后面的句子不发生任何其他的变化。倒装句共四种形式：

　　1. He is so tall that he cannot sit in the first row.

　　改成 So tall is he that he cannot sit in the first row.

　　2. He can do it so quickly that he earns most.

　　改成 So quickly can he do it that he earns most.

　　3. He has done it so quickly that he gets the prize from the manager.

　　改成So quickly has he done it that he gets the prize from the manager.

　　4. He gets the highest mark so easily that he often looks down upon those industrious students.

　　改成So easily does he get the highest mark that he often looks down upon those industrious students.

　　把动词分成四种，前三种(系动词、情态动词以及完成时态)将系动词、情态动词以及构成完成时态的助动词(have，has，had)倒装;第四种实义动词，用助动词do以及其变体进行倒装。

　　三、时间状语从句

　　常用的时间状语从句：not...until，since，as soon as，hardly...when，no sooner...than...

　　这里重点讲解hardly...when...，以及no sooner...than...

　　I had hardly got back to the kitchen when the telephone rang.(过去完成时，过去时)

　　我刚离开厨房，电话就响了。

　　改成倒装句：

　　Hardly had I got back to the kitchen when the telephone rang.

　　Hardly had the news spread around the country when the president came up with another idea to get a higher efficiency.

　　四、条件状语从句

　　引导条件状语从句的词：if，provided that，providing that

　　If the government takes immediate steps to curb this situation, the general public will trust the government again.

　　可以将if改成provided that，也可以改成providing that。