It is [urgent/necessary/convenient/desirable/advisable] for sb. to do sth.

　　have [trouble/a difficult time] [in doing sth./with sth.]

　　举例证：It can be given by a (well known/concrete) example that ____________. / In order to see this point clearly, let us to see an example:____________/To illustrate this, there is an example that is very persuasive:____________.

　　第一点原因：

　　The main/first reason is that ____________.

　　First, we can observe easily that in modern society, ...

　　In the first place

　　To begin with, (a good roommate should ____________)

　　第二点原因：

　　Besides, the further reason why I advocate AAA is that ____________.

　　[The second/another] reason for [my/people’s] propensity for A is that ____________

　　[The second/another] desirable quality for a good roommate is that ____________

　　第三点原因：

　　Moreover,____________

　　The third reason, [not the last/however], goes this way: ____________

　　写完三条原因还可以再写：Maybe there are some other reasons( to show____________). But

　　it is generally believed that the reasons mentioned above are commonly acceptable.

　　最后意犹未尽或者字数不够可以加这么一句：

　　Nevertheless I must admit that people can do well without AAA, but no one can ignore the additional convenience and satisfaction offered by AAA. Such experience will definitely be helpful in one’s later life.

　　一个使用了模板的例子：

　　对立观点：

　　In this modern society, people always confront the dilemma of choosing whether AAA or BBB. This problem is a much debated one in that it affects everybody in his or her daily life. People may prefer one to the other although some may have no opinions about either at all. Before rendering my opinion, I think it is necessary to take a glance at the arguments on both sides.

　　It is quite rational for average people to choose BBB because of the obvious reason that 原因.The most extreme manifestation of this idea is the fact that 例子.Even so, however, many advantages of BBB over AAA will be obscured by its considerable drawbacks such as 例子.Therefore we have no complete evidence to suggest that BBB is always better than AAA. Moreover, a close scrutiny of the potential benefits of choosing AAA would reveal how flimsy it is to stick to the propensity to BBB over AAA.

　　There are numerous reasons for my preference for AAA, and I shall here explore only a few of the most important ones. One chief reason is that 原因一.And I can think of no better illustration of the idea than the fact that 例子一. The above is only part of the important aspects, and another one with equal significance with respect to choosing between the two lies in the development of the proposition that 原因二. This well explains the undeniable fact that 例子二. Besides, a further reason why I advocate AAA is that 原因三.This may explain why 例子三.

　　Last but not least, there is also a more practical reason why I would choose AAA, that is 原因四.

　　All in all, taking into account all these merits that AAA boasts of, we may safely arrive at the conclusion that the advantages of AAA outweigh any benefit we can get from BBB and choosing AAA is a rather wise decision.