为什么不能
<select >
<option value="">--请选择--</option>
<option value="111">111</option>
<option value="222">222</option>
</select>
<select >
<option value="">--请选择--</option>
<option value="111">111</option>
<option value="222">222</option>
</select>
<select >
<option value="">--请选择--</option>
<option value="111">111</option>
<option value="222">222</option>
</select>
<option value=""> </option>
<option value="111">111</option>
<option value="222">222</option>
</select>
<option value="111" selected="true">111</option>
<option value="222">222</option>
</select>
<select >
<option value=""> </option>
<option value="111">111</option>
<option value="222">222</option>
</select>