(四)原因解释型
　　1. 给出一个事实,要求解释它的原因.

　　陈述这个事实 As is know by all, ……

　　Among countless factors which contribute to XXX, there exist three most conspicuous ones:

　　One of the primary causes is that…

　　XXX also results from…

　　… is responsible for xxx, as well.

　　To put all into a nutshell, I draw the conclusion that A,B and C are three main contributors to XXX

　　2. What should we do? How do something influence our lives? what are the characters of something.

　　背景描述

　　There are numerous approaches to solving…/impacts on sth. /characteristics of… , and I would explore the most conspicuous ones there.

　　One of the primary method, to my mind, is that…

　　one of the primary impact, to my mind, is that…

　　one of the primary characteristic, to my mind, is that…

　　a more subtle point which we must consider is that…

　　In addition/ furthermore ……

　　In conclusion, Taking into account of all these methods/ affects / aspects, we may reach the conclusion that……