虚拟语气：
英语中的语气分为陈述语气、祈使语气、虚拟语气三类。虚拟语气用来表示假想，而不表示客观存在的事实，所说的是一个条件，不一定是事实，或与事实相反。虚拟语气通过谓语动词的特殊形式来表示。
1. If sb had done sth (坏事)， sb would never have done sth (好事).
如果某人过去做了某事(坏事)，那么他永远不可能做某事。
If Hugh Miller， after toiling all day in quarry (采石场)， had devoted his evenings to rest and recreation， he would never have become a famous geologist.
2. Sb would never have done sth (好事1) ， never have done sth (好事2)， if sb had done sth (坏事)
某人永远不可能做某事，永远不可能做某事，如果某人过去做了某件坏事。
The celebrated mathematician， Edmund Stone， would never have published amathematical dictionary， never have found the key to science of mathematics， if he had given his spare moments to idleness.
3. Had sb done sth(坏事) ，sb would never have done sth (好事)
如果某人过去做了某件坏事，而不是去做某件好事，那么他永远不可能做某事(好事)。
Had the little Scotch lad， Ferguson， allowed the busy brain to go to sleep while he tended sheep on the hillside， instead of calculating the position of the stars by a string of beads， he would never have become a famous astronomer.
对以上几个虚拟语气的应用范文：
Group discussion Google
If Google had ignored the importance of group discussion， this high-tech company would never have achieved today's stunning success.
(If sb had done sth， he would never have done sth)
Google， a once obscure， ailing / fragile company， would never have achieved today's stunning success， never have conquered so big a market share， if it had ignored the importance of group discussion.
(sb would never have done sth ， never have done sth ， if sb had donesth)
Had Google ， a once small ， obscure company ， ignored the importance of group discussion ，the hi-tech tycoon would never ， never have harvested today's overwhelming success . (压倒性的成功)
情态动词：
情态动词本身有一定的词义，但是不能独立作谓语，只能和行为动词一起构成谓语。情态动词用在行为动词前，表示说话人对这一动作或状态的看法或主观设想。 情态动词虽然数量不多，但用途广泛，主要有下列： can (could)， may (might)， must， need， ought to， dare (dared)， shall (should)， will (would) must not.
雅思写作中关于情态动词的使用经常存在漏用和误用的情况，而大作文本身就是要求写对某个事物或者现象的评价，所以不可避免要出现带有情态动词的观点句。下面是发现的比较常见的问题：
首先是情态动词，尤其是Will的漏掉。
中国考生受汉语影响，一提到“将来”才会有意识地用will， 实际上will可以表达“能、将、会、要、就”等多种意义。只是涉及到这样的地方很多考生就把这几个词当作虚词忽略掉了，以至于经常出现“观点”与“事实”不分的句子， 如：
Riding bicycles reduces air pollution.
如果没有情态动词，这个句子就只表示目前存在的状态或者事实，而不表示个人对骑自行车的评价。
其它的常见的漏用还体现在与if引导的状语从句一起连用的主句中，so that或者in order that引导的从句，或者是与without， in case of等介词短语连用的主句，不论条件还是目的都是写作中经常出现的句式。如：
If I have time tomorrow， I drive to pick you up.
Xiao Zhang gets up very early so that he catches the earliest bus to work.
Without enough time to stay inside campus， college students don't have time to improve themselves.
其次是情态动词“can”的误用。
分析认为主要问题是中国学生在亮观点时对“can”情有独钟，而英式的学风历来讲究严谨，像can这样语气过于绝对的表达最好换成may/ will， 或者是语气更委婉的might/would probably等，同时还要搭配一定程度的副词，如：
Over indulgence in computer games can lead to social violence especially of teenagers.
上句中can不如might用起来更加客观，因为几乎每个小孩都玩游戏，但绝不是每个人都会犯罪。
另外一个容易误用的词是should。
多表示根据社会风俗习惯个人的责任，而在比较正式的议论文写作中，多数句子是以客观事物做主语的，所以用should就有些不太恰当，如：
To tackle the problem of youth crimes related with computer games， advertisement enterprises should restrict the large-scale promotion.
一般我们会用另外一个更客观性的短语be to do来代替，或者是shall，但是这里的shall不是用于第一人称后的将来时符号，而表示的是一种情态。
至于must， 因为语气实在强硬，所以一般在社会性的问题的论述上我们要慎用，建议考生可换成need/ shall/ be to do或者是be expected to do形式。如：
To help students get better employment， universities must increase the skillful courses.
虽然情态动词不是关系写作是否能上6分的语法项目，但也会在一定程度上影响到分数，所以希望考生们能引起足够的重视。
