This phenomenon exists for a number of reasons. First, … Second, … Third, …
這一現象的存在是有許多原因的.首先，……；第二,，……；第三，……
Why did …? For one thing …，for another …. Perhaps the primary reason is…
為什麼會……？一個原因是……，令一個原因是……；或許其主要原因是……
I quite agree with the statement that … The reasons are chiefly as follows.
我十分贊同這一論述,即……，其主要原因如下:
