ㄧ.Forms:選擇功能表
<body data-spy="scroll" data-target="#nav-demo">
  <div class="component" id="demo" style="height: 300vh">
    <select id="demo-select" class="form-control">
      <option value="a">A</option>
      <option value="b">B</option>
      <option value="c">C</option>
    </select>
  </div>
</body>
.demo.component{
  padding: 50px;
}
重點: