I am taking an online [English skill test](http://www.cambridgeenglish.org/test-your-english/adult-learners) and noticed there's a question like this:

> 
> \_\_\_ you get your father's permission, I'll take you skiing next weekend.
> 
> 
> (As) OR (Provided)
> 
> 
> 

The correct answer is `Provided` according to the page. I am wondering why `As` is not ok for this case?