Jquery logic if x checkboxes ticked show div quiz
===

I know this is a simple and lame thing. I need to build a small form where if the user checks 1 checkbox show div a, if two are checked show div b and if three or more are checked show div c. 

Any ideas on a simple jQuery way of doing this, I have tried and am overcomplicating this to no avail.

Thanks in advance and sorry for a nooby question!