提出原因：
there are many reasons for ...
why .... , for one thing,...
the answer to this problem involves many factors.
any discussion about this problem would inevitably involves ...
the first reason can be obiviously seen.
most people would agree that...
some people may neglect that in fact ...
others suggest that...
part of the explanation is ...

进行对比：
the advantages for a for outweigh the disadvantages of...
although a enjoys a distinct advantage ...
indeed , a carries much weight than b when sth is concerned.
a maybe ... , but it suffers from the disadvantage that...

承上启下：
to understand the truth of ..., it is also important to see...
a study of ... will make this point clear

让步：
certainly, b has its own advantages, such as...
i do not deny that a has its own merits.

结尾：
>from what has been discussed above, we may safely draw
the conclusion that ...
in summary, it is wiser ...
in short...

在作文中引用合适的名言警句，会给你的文章增色许多。这里收集了我本人喜爱的一些名言，可能会对你有用。我们使用引用的位置可以在开头结尾或正文段落中，
常见的使用形式如下：
one of the greatest early writers said ...
"knowledge is power", such is the remard of ...
"......". that is how sb comment ( criticize/ praise...).
"......". how often we hear such words like there.
useful quotations

逆境
by robert collier
in every adversity there lies the seed of an equivalent advantage. in every defeat there is a lesson showing you how to win the victory next time.

努力与成功
by ann landers
opportunities are usually disguised as hard work, so most people don't recognize them.

坚持
by ralph waldo emerson
no one can cheat you out of ultimate success but yourselves.