How to make a choice option disappear/change once used?

Hey there! I am an RPG Maker noob, and could really do with some help. 

I have in my game a character which asks you something, and if you pick the first answer the character gives you an item.
I would like to know how to make the answer where you receive an item disappear once it has been chosen so players don't keep going back and getting the item numerous times.
 

Here's what I have so far:



(Also I'm making this game for a school project, so don't look to closely at the question/answer, it's meant to be stupid)

You'll need switches and multiple pages on the event.


I suggest you search for a game called "variables guide", that will help you in several ways (you can also follow the link in my signature and read there, the variables guide is also linked there)

Thanks!

Himeworks has a script for this. It costs money for commercial use, but it's great. It's for actually disabling choices. Your example is really simple though, and looks like you probably want to simply activate a self-switch and change the page, giving you completely different dialogue.