//设置单选下拉框选中
$("input:eq(0)").click(function () {
    $("#single option").removeAttr("selected"); //移除属性selected
    $("#single option:eq(1)").attr("selected", true); //设置属性selected
});
//设置多选下拉框选中
$("input:eq(1)").click(function () {
    $("#multiple option").removeAttr("selected"); //移除属性selected
    $("#multiple option:eq(2)").attr("selected", true); //设置属性selected
    $("#multiple option:eq(3)").attr("selected", true); //设置属性selected
});
//设置单选框和多选框选中
$("input:eq(2)").click(function () {
    $(":checkbox").removeAttr("checked"); //移除属性checked
    $(":radio").removeAttr("checked"); //移除属性checked
    $("[value=check2]:checkbox").attr("checked", true); //设置属性checked
    $("[value=check3]:checkbox").attr("checked", true); //设置属性checked
    $("[value=radio2]:radio").attr("checked", true); //设置属性checked
});