Help with Jquery/Json

/*!
* Easy jQuery-Based Quiz ~ Copyright (c) 2012 Meredith Dodge, http://meredithdodge.com
* Released under MIT license
*/

//The path to your images
var imgpath = "images/";
//The path to your json
var jsonpath = "json/";
//The filename will be determined by the rel attribute on div#quiz
var jsonfile = "";

$(document).ready(function () {
    //Make sure radio buttons are not disabled or checked (helpful when refreshing)
    $("input[type='radio']").attr("disabled", false);
    $("input[type='radio']").attr("checked", false);
    $(".submit").click(function (e) {
        e.preventDefault();
        //Check the quiz results
        checkQuiz();
    });
    //Build the json filename
    jsonfile = $("#quiz").attr("rel") + ".json";
});

//Load json file
function getData(update) {
    $.getJSON(jsonpath + jsonfile, function (json) {
        //Execute the callback
        update(json);
    }).error(function () { alert("error"); });
}

function checkQuiz() {
    $(".submit").remove();
    getData(function (data) {
        var ans = data.key;
        var result = {};
        $(".question").each(function () {
            //Get the question id
            var _q = $(this).attr("id");
            //Get the selected answer class
            var _a = $("#" + _q + " input:checked").closest("li").attr("class");
            //Add the values to the result object
            result[_q] = _a;
            //Indicate the correct answer
            $("#" + _q + " ." + ans[_q]).append("<img src='" + imgpath + "circle.png' class='png_bg' alt='correct answer'>");
            //Compare the selected answer with the correct answer
            if (ans[_q] == _a) {
                $(this).addClass("correct");
            } else {
                $(this).addClass("wrong");
            }
        });
        //Build the feedback
        var fdbck = "You got " + $(".correct").length + " out of " + $(".question").length + " correct. "
        if ($(".correct").length == 0) {
            fdbck += "Better luck next time.";
        } else if ($(".correct").length > $(".question").length / 2) {
            fdbck += "Good job!";
        } else {
            fdbck += "Not bad.";
        }
        $(".feedback").text(fdbck);
        $(".feedback").show();
    });
}

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