<div class="answer">

                    <ul id="ul1">

                        <span>答案：</span>

                        <input name="radio" type="radio" value="" id="1" onclick="radio_click('ul1',1)"

                            class="nav_1" />

                        <label class="btn_1" value="" onclick="lable_click('ul1',1,1)">

                        </label>

                        <input name="radio" type="radio" value="" id="2" onclick="radio_click('ul1',2)"

                            class="nav_1" />

                        <label class="btn_2" value="" onclick="lable_click('ul1',2,2)">

                        </label>

                        <input name="radio" type="radio" value="" id="3" onclick="radio_click('ul1',3)"

                            class="nav_1" />

                        <label class="btn_3" value="" onclick="lable_click('ul1',3,3)">

                        </label>

                        <input name="radio" type="radio" value="" id="4" onclick="radio_click('ul1',4)"

                            class="nav_1" />

                        <label class="btn_4" value="" onclick="lable_click('ul1',4,4)">

                        </label>

                    </ul>