This phenomenon exists for a number of reasons. First, … Second, … Third, …
这一现象的存在是有许多原因的.首先, … 第二, … 第三,…
Why did… ? For one thing… For another…. Perhaps the primary reason is…
为什么会…? 一个原因是… 令一个原因是…或许其主要原因是….
I quite agree with the statement that… the reasons are chiefly as follows.
我十分赞同这一论述,即…