<div class='form-group'>
 <label class='col-md-2 control-label'>题型</label>
 <div class='col-md-2'>
  //通过fn()函数去改变答案框状态的改变
  <select class="form-control input-sm" id="type" onclick="fn()">
    <option value="选择题">选择题</option>
  <option value="判断题">判断题</option>
  <option value="多选题">多选题</option>
  </select>
 </div>
</div>
 
 
<div class='form-group'>
 <label class='col-md-2 control-label'>正确选项</label>
 <div class='col-md-10'>
//此处写一个下拉框一个input框，当题型为多选时，利用JS将下拉框隐藏，input框显示
 <input class='form-control' placeholder='正确选项' type='text' name='answerTrue1' id='answerTrue1' type="hidden" data-bv-notempty='true' data-bv-notempty-message='正确答案不能为空'>
 <select class="form-control input-sm" id="answerTrue2" name="answerTrue2">
 <option value="A">A</option>
 <option value="B">B</option>
 <option value="C">C</option>
 <option value="D">D</option>
 </select>
 </div>
</div>

<script type="text/javascript">
//页面加载时执行init函数，使多选题的正确答案的文本框隐藏
init();
function init（）{
 $("#answerTrue1").hide();
}
 
//题目类型和答案选择的二级联动
 function fn(){
 var type=document.getElementById("type");
 var t=type.value;
 var answer=document.getElementById("answerTrue2");
 switch(t)
 {
  //判断是选择题还是判断题，然后改变下拉框中的内容
  case "选择题": answer.innerHTML="<option>A</option><option>B</option> 
          <option>C</option><option>D</option>";
  $("#answerTrue1").hide();
  $("#answerTrue2").show();
  break;
  case "判断题":answer.innerHTML="<option>正确</option><option>错误</option>";
  $("#answerTrue1").hide();
  $("#answerTrue2").show();
  break;
  default:$("#answerTrue1").show();
  $("#answerTrue2").hide();
 }
 };
</script>