关键同和段首句一样.起到了指导文章思路的作用，考生主要通过分析所给的关键词或词组去揣摩文章中心内容，明确短文的要点，把所给的词或词组自然地运用到自己的作文中.
关键词的作用在于提示作文的主题和内容.此类文章的发挥余地较大，并且为考生提供了语言素材。难度在于考生需要从所有词语中找出内在联系，确定文章的主题、结构和内容。关键词作文有利于培养作者的构思能力和语言组织能力。作者在进行写作的时候要认真分析，运用自己的知识和想象力，写出符合要求的短文。短文中内容方面比较重要的词语。关键词的分析有助于我们对短文主要内容做出判断。
英语四级作文加分句推荐
一、~~~ the + ~ est + 名词 + (that) + 主词 + have ever + seen ( known/heard/had/read, etc) ~~~ the most + 形容词 + 名词 + (that) + 主词 + have ever + seen ( known/ heard/ had/ read, etc)
例句：Helen is the most beautiful girl that I have ever seen.
海伦是我所看过最美丽的女孩。
Mr. Chang is the kindest teacher that I have ever had.
张老师是我曾经遇到最仁慈的教师。
二、Nothing is + ~~~ er than to + V Nothing is + more + 形容词 + than to + V
例句：Nothing is more important than to receive education.
没有比接受教育更重要的事。
三、~~~ cannot emphasize the importance of ~~~ too much.(再怎么强调...的重要性也不为过。)
例句：We cannot emphasize the importance of protecting our eyes too much.
我们再怎么强调保护眼睛的重要性也不为过。
四、There is no denying that + S + V ...(不可否认的...)
例句：There is no denying that the qualities of our living have gone from bad to worse.
不可否认的，我们的生活品质已经每况愈下。
五、It is universally acknowledged that + 句子~~ (全世界都知道...)
例句：It is universally acknowledged that trees are indispensable to us.
全世界都知道树木对我们是不可或缺的。
六、There is no doubt that + 句子~~ (毫无疑问的...)
例句：There is no doubt that our educational system leaves something to be desired.
毫无疑问的我们的教育制度令人不满意。
七、An advantage of ~~~ is that + 句子 (...的优点是...)
例句：An advantage of using the solar energy is that it won't create (produce) any pollution.
用太阳能的优点是它不会制造任何污染。
八、The reason why + 句子 ~~~ is that + 句子 (...的原因是...)
例句：The reason why we have to grow trees is that they can provide us with fresh air./ The reason why we have to grow trees is that they can supply fresh air for us.
我们必须种树的原因是它们能供应我们新鲜的空气。
九、So + 形容词 + be + 主词 + that + 句子 (如此...以致于...)
例句：So precious is time that we can't afford to waste it.
时间是如此珍贵，我们经不起浪费它。
十、Adj + as + Subject(主词)+ be, S + V~~~ (虽然...)
例句：Rich as our country is, the qualities of our living are by no means satisfactory. {by no means = in no way = on no account 一点也不}
虽然我们的国家富有，我们的生活品质绝对令人不满意。
十一、The + ~er + S + V, ~~~ the + ~er + S + V ~~~
The + more + Adj + S + V, ~~~ the + more + Adj + S + V ~~~(愈...愈...)
例句：The harder you work, the more progress you make.
你愈努力，你愈进步。
The more books we read, the more learned we become.
我们书读愈多，我们愈有学问。
十二、By +Ving, ~~ can ~~ (借着...，..能够..)
例句：By taking exercise, we can always stay healthy.
借着做运动，我们能够始终保持健康。
十三、~~~ enable + Object(受词)+ to + V (..使..能够..)
例句：Listening to music enable us to feel relaxed.
听音乐使我们能够感觉轻松。
十四、On no account can we + V ~~~ (我们绝对不能...)
例句：On no account can we ignore the value of knowledge.
我们绝对不能忽略知识的价值。
十五、It is time + S + 过去式 (该是...的时候了)
例句：It is time the authorities concerned took proper steps to solve the traffic problems.
该是有关当局采取适当的措施来解决交通问题的时候了。
十六、Those who ~~~ (...的人...)
例句：Those who violate traffic regulations should be punished.
违反交通规定的人应该受处罚。
十七、There is no one but ~~~ (没有人不...)
例句：There is no one but longs to go to college.
没有人不渴望上大学。
十八、be + forced/compelled/obliged + to + V (不得不...)
例句：Since the examination is around the corner, I am compelled to give up doing sports.
既然考试迫在眉睫，我不得不放弃做运动。
十九、It is conceivable that + 句子 (可想而知的)
It is obvious that + 句子 (明显的)
It is apparent that + 句子 (显然的)
例句：It is conceivable that knowledge plays an important role in our life.
可想而知，知识在我们的一生中扮演一个重要的角色。
二十、That is the reason why ~~~ (那就是...的原因)
例句：Summer is sultry. That is the reason why I don't like it.
夏天很燠热。那就是我不喜欢它的原因。