<!-- 1.45option、optgroup和select标签-->
<select>
<optgroup label="China">
<option value="三环">sanhuan</option>
<option value="五菱">wuling</option>
</optgroup>
<optgroup label="Deutsch">
<option value="BMW">宝马</option>
<option value="Dercedes">奔驰</option>
</optgroup>
</select>
<select>
<optgroup label="China">
<option value="三环">sanhuan</option>
<option value="五菱">wuling</option>
</optgroup>
<optgroup label="Deutsch">
<option value="BMW">宝马</option>
<option value="Dercedes">奔驰</option>
</optgroup>
</select>
