【示例一】
　　①There are many reasons responsible for this phenomenon/case/instance and the following are the typical ones. ②The first reason is that  ________（理由一）. ③The second reason is that ________（理由二）. ④The third reason is that/A case in point is that/The typical example is that ________（理由三）.
　　【示例二】
　　①There are many reasons to explain/explaining the effect/phenomenon/case/instance. ②The most contributing one is/the main reason is no other than  ________（理由一）. ③What is more, ________（理由二）. ④ ________（理由三）also play a role in this case.