x
1
<select>2
<optgroup label="分组 1">3
<option>选项 1.1</option>4
</optgroup> 5
<optgroup label="分组 2">6
<option>选项 2.1</option>7
<option>选项 2.2</option>8
</optgroup>9
<optgroup label="分组 3" disabled>10
<option>选项 3.1</option>11
<option>选项 3.2</option>12
<option>选项 3.3</option>13
</optgroup>14
</select>15