描述流程的文章，应说明：
1. 首先说明是做什么工作的过程，目的是什么
2. 按时间/过程先后描述
3. 简单总结
描述流程常用句子：
The following diagraph shows the structure of……
The picture illustrates……
It mainly consists of……
It works as follows.
It always involves the following steps.
The whole procedure can be divided into…stages.
描述流程常用过渡性词语：
firstly
secondly
thirdly/finally
the first step is to
the next step is to
the last step is to
the first stage involves
in the next stage
in the following stage
in the last stage
first of all
to begin with
next
then
later
at the same time
simultaneously
subsequently
consequently
before this
during
after this
in the course of
in order to/in order not to
in order that
so as to/so as not to