Hi I have a javascript quiz (thanks to Pullo's guidance), and

now Id like to change to radio buttons with around 3 or 4 options, like for example:

Join the 2 sentences:

Mary is English. She was born in London

Radio buttons: "A". Mary was born in England
"B" Mary, who is English, was born in London
"C" English Mary was born in London
"D" London Mary is English born

So, I was thinking of around 10 questions in the quiz , with a submit button at the bottom, and a "tick" after correct answers, and "x" after incorrect answers.

Or, maybe to put it another way, how could I modify the following code, replacing the dropdown menus with radio buttons?

Code:
 <form action="#" method="post" id="myForm" name="f">
              <ol>
                <li>
            I think blue is the colour that  &nbsp;
         
                  <select name="question1">
                    <option value="na"> </option>
                    <option value="a"> optional </option>   
                    <option value="b"> necessary</option>
                    
                    
                  </select>  
                   I like best.
                </li>
                <li>
                  Simon, who &nbsp;
                  
              
                  <select name="question2">
                   <option value="na"> </option>
                    <option value="a"> optional </option>   
                    <option value="b"> necessary</option>
                     
                  </select>
                 is 25, got married last week.
          
                </li>
                <li>
                 My car has a mechanical problem that / which &nbsp;
                  
             
                  <select name="question3">
                   <option value="na"> </option>
                    <option value="a"> optional </option>   
                    <option value="b"> necessary</option>
                  </select> 
                   is expensive to repair.
                </li>
                <li>
              He left the keys that &nbsp;
               
            
                  <select name="question4">
                   <option value="na"> </option>
                   <option value="a"> optional </option>   
                    <option value="b"> necessary</option>
                  </select> 
                 I gave him on the table.
                </li>
                <li>
                 The carpenter who / that  &nbsp;
                 
                
                  <select name="question5">
                   <option value="na"> </option>
                    <option value="a"> optional </option>   
                    <option value="b"> necessary</option>
                      
                      
                  </select> 
                    made my furniture is very rich.
                </li>
                <li>
                
                He took a plane that  &nbsp;
                  <select name="question6">
                   <option value="na"> </option>
                    <option value="a"> optional </option>   
                    <option value="b"> necessary</option>
                        
                  </select> 
             left from London.
                
                </li>
                <li>
                The money that / which  &nbsp;
                  <select name="question7">
                 <option value="na"> </option>
                    <option value="a"> optional </option>   
                    <option value="b"> necessary</option> 
                  </select> 
                you borrowed was not really necessary.
                </li>
                <li>
                      James is the most honest person that &nbsp;
                  <select name="question8">
                   <option value="na"> </option>
                     <option value="a"> optional </option>   
                    <option value="b"> necessary</option>
                     
                  </select> 
                   I've ever met.  
                </li>
                <li>
               They're the people who /that &nbsp;
                  <select name="question9">
                   <option value="na"> </option>
                 <option value="a"> optional </option>   
                    <option value="b"> necessary</option>
                  </select> 
                         live next door.
                </li>
                <li>
            The idea, which &nbsp;
                  <select name="question10">
                  <option value="na"> </option>
                     <option value="a"> optional </option>   
                    <option value="b"> necessary</option>
                      
                  </select> 
              was very original, has been accepted.
                </li>
                
                <li>
           The book that / which &nbsp;
                  <select name="question11">
                  <option value="na"> </option>
                     <option value="a"> optional </option>   
                    <option value="b"> necessary</option>
                      
                  </select> 
            I bought is very interesting.
                </li>
              </ol>
            
             
              <div id="buttons">
             <input type="submit" id="submit" value="Result" />
              <input type="reset" class="reset" id="reset" name="reset" value="Start again" /> 
            </form>  </div>  </div> 
             <div id="score"></div> 
               <div class="address">





  John Kelly &copy; 2006 - 2013
        
</div>
          </div> 
        </div> 
      </div> 
    </div>
    
    
    
    
    
    
 <script>
      Object.size = function(obj) {
        var size = 0, key;
        for (key in obj) {
          if (obj.hasOwnProperty(key)) size++;
        }
        return size;
      };
      
      (function(){
        "use strict";
        window.checkAnswers = function(opts){
          
          function validateInput(){
            var question,
                answer;
                
            for (question in opts) {
              if(opts.hasOwnProperty(question)) {
                answer = f.elements[question].options[f.elements[question].selectedIndex].value;
                if(answer === "na"){
                  opts[question].state = "not-filled-in";
                } else if(answer === opts[question].answer){
                  opts[question].state = "correct";
                } else {
                  opts[question].state = "error";
                }
              }
            }
          }
          
          function markCorrectOrIncorrect(){
            var question, 
                li;
            
            for (question in opts) {
              if(opts.hasOwnProperty(question)) {
                var img = new Image(),
                li = f.elements[question].parentElement,
                feedbackImg = li.getElementsByTagName('img')[0];

                if (feedbackImg){
                  li.removeChild(feedbackImg);
                }
                
                if(opts[question].state === "correct"){
                  img.src = "http://www.littletherese.com/tick.jpg";
                  li.appendChild(img)
                } else if(opts[question].state === "error"){
                  img.src = "http://www.littletherese.com/x.jpg";
                  li.appendChild(img)
                }
              }
            }
          }
          
          function displayScore(){
            var correct = 0,
                error = 0,
                score = document.getElementById("score"),
                totalQuestions = Object.size(opts),
                question;

            for (question in opts) {
              if(opts.hasOwnProperty(question)) {
                if(opts[question].state === "correct"){
                  correct ++
                } else if(opts[question].state === "error"){
                  error ++
                }
              }
            }
            score.innerHTML = "You got " + correct + " out of " + totalQuestions;
          }
          
          function init(){
            validateInput();
            markCorrectOrIncorrect();
            displayScore();
          }
          
          init();
        }
      }());

      f.onsubmit = function(){
        checkAnswers({
        question1: {answer: "a"},
          question2: {answer: "b"},
          question3: {answer: "b"},
          question4: {answer: "a"},
          question5: {answer: "b"},
          question6: {answer: "b"},
          question7: {answer: "a"},
          question8: {answer: "a"},
          question9: {answer: "b"},
          question10: {answer: "b"},
          question11: {answer: "a"},
        })
        return false;
      }
      
      f.reset.onclick = function(){
        location.reload();
      }
    </script> 
  </body>
</html>
Thanks for any help!