1:The reason why + 句子 ~~~ is that + 句子 (...的原因是...)
2:This phenomenon exists for a number of reasons .First,…….Second,…….Third,……。這一現(xiàn)象存在有很多原因的,第一……第二……第三……
3:For one thing,…… For another thing,…… ==On the one hand,……On the other hand……一方面……另一方面……
4: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。