function grade(){
    var nCorrect = 0;
    
    for(var i = 0; i < correctAnswers.length; i++){
        if(answers[i] == correctAnswers[i])
            nCorrect++;
        
        var answerTextTag = document.getElementById("p" + (i + 1));
        answerTextTag.appendChild(document.createTextNode("Correct Answer is: " + 
                                                          correctAnswerTexts[i]));
    }
    
    alert("You correctly answered " + nCorrect + 
        " questions out of " + correctAnswers.length);
}

function clearAnswers(){
    for(var i = 0; i < correctAnswers.length; i++){
        answers[i] = null;
        
        var answerTextTag = document.getElementById("p" + (i + 1));
        var children = answerTextTag.childNodes;
        for(var j = 0; j < children.length; j++){
            answerTextTag.removeChild(children[j]);
        }
        
        var formElements = window.document.questionForm.elements;
        for(j = 0; j < formElements.length; j++){
            if(formElements[j].type == "radio"){
                formElements[j].checked = false;
            }
        }
    }
}

function setAnswer(index, ans){
    answers[index] = ans;
}