I see a couple of options here, ASP is server side, so you are gonna run into the issue of either reloading the page, or having you answer somewhere in the code. If you are going the reload path, then you just need to have the user submit the form, either when they click the radio or with a button, something like:
<form method=post action=checkanswer.asp name=question><input type=radio name=answer1 onclick=document.question.submit()></form>
Or you can go the javascript route, and put the answer in the page with:
content = "<script language=javascript> function CheckAnswer(a){
if(a == 2){ alert("You are correct"); }
}</script>
Now its not all that simple, you have to work out the details, but that is gist of it. If you are testing people for some other reason than fun, I would go the ASP route and load a result page with something like "Yeah your correct" or "Nope try again", or however you want to put it to them. The ASP route just means you can't open the source of the page and cheat. There are a few other, more complicated ways to do this with java, but why when all it costs you is page load. Post up if you need more help.