<!DOCTYPE html>
<html>
<head>
 <meta charset='utf-8'>
 <title> Quiz </title>
</head>
<body>
 <table>
  <tr>
   <td colspan=2 id='score'> 0
  <tr>
   <td colspan=2 id='msg'>  Click go to start.
  <tr>
   <td><input type='radio' name='q' id='ca'> <td id='a'>
  <tr>
   <td><input type='radio' name='q' id='cb'> <td id='b'>
  <tr>
   <td colspan=2 id='response'>
 </table>
 <button onclick='go();'> Go </button>
 <script>
 var Q = [
  {msg: "A or B", a: "A", b: "B", ans: "a"},
  {msg: "B or A", a: "B", b: "A", ans: "b"}
 ];
 var qidx = -1;
 var score = 0;

 function wronganswer() {
   get("response").innerHTML = "Incorrect";
 }
 function rightanswer() {
   score++;
   get("score").innerHTML = score;
   get("response").innerHTML = "correct";
 }
 
 function get(x) {
   return document.getElementById(x);
 }
 function go() {
   var msg = get("msg");
   var ca = get("ca"), cb = get("cb");
   var a = get("a"), b = get("b");
   
   if (qidx != -1) {
     if (Q[qidx].ans == "a") {
       if (ca.checked == false) wronganswer();
       else rightanswer();
     } else {
       if (cb.checked == false) wronganswer();
       else rightanswer();
     }
   }
   qidx++;
   msg.innerHTML = Q[qidx].msg;
   a.innerHTML = Q[qidx].a;
   b.innerHTML = Q[qidx].b;
 }
 </script>
</body>
</html>