747 复习
How about + 从句（一般现在时）?
How about I pick you up at eight o'clock?
How about/what about + 名词/名词短语（食物、饮料）
What about a coffee?

why not …? 
why don't …?

我们可以用 why not …? 提出一般性建议。
We can use why not …? to make a general suggestion.
general 一般性的，普通的；大致的，大体的；总体的，普遍的

Why not …? 常用于广告语：
Why not take a break in the south-west?
为什么不到西南部休息一下呢？
Why not treat yourself to a meal at the Icon Restaurant?
为什么不请自己在Icon餐厅吃一顿呢？

specific 具体的，明确的，确切的；特定的，特有的
general <—> specific

我们可以用 why don't …? 提出具体建议。
We can use why don't …? to make a specific suggestion.

You look really tired. Why don't you take some time out and rest?
你看起来很累，出去休息一会儿吧。

It's getting late in the evening now. Why don't we stop now and work on this tomorrow morning?
现在已经很晚了，我们先做到这儿，明天早上再做。