in my mind , the following factors/reasons/causes need to be taken into consideration.

我认为，我们需要考虑下列因素/原因：

There are several reasons for this phenomenon/why…-(as follows).

造成这种现象的原因如下：

And I would like to present two explanations for this:

对于此，我有如下两点愚见：

The reasons are chiefly as follows. 主要原因如下：

There are numerous reasons why ____, and I would like to explore a few of the most important ones here.

为什么___________，原因很多，在此列举几个较为重要的原因。

The reasons are presented below. 原因如下。

There are three premier(主要的)/best/ most important, largest, significant, obvious, crucial causes as follows.

以下这些是造成这一问题的最主要/最好/最重要/最大/最有意义/明显/至关重要的原因。

This is based on the propensity(倾向，原因) of following points.

这基于以下的原因。

The main reason is that.. 主要原因是_____________。

One very important argument for ….. is that….

_______的非常重要的原因便是____________________。

The reasons are quite clear. Above all, ….

原因非常清楚。首先(首要的是)__________。

The first reason can be seen by every person.

第一个原因其实很明显。

The first and most important reason is that…..

第一个而且最重要的原因是______________。

One of the reasons that are given for….is that….

______________的原因之一是__________________。