求Preposition ”for” 和 ”as” 的用法

1. For(為了,給予)
eg. I am looking for my purse.
Eating more vegetables is good for our healthly.
A pencil is used for writing.
I have a present for you.
I am waiting for you.
2. As(就是或好像)
eg. He works as a manager in this company.
My sister dresses up as a witch at Halloween.(