2A What about washing the car on Sunday?
2B Why don't wash the car on Sunday?
2C Let's wash the car on Sunday.
3A We'll plant more trees around the school so that it will look more beautiful.
3B We'll plant more trees around the school in order that it will look more beautiful.
3C We'll plant more trees around the school so as to make it look more beautiful.
why don't we wash~
What about washing the car on sunday?
这个很容易的
。。