HtmlSelect' cannot have children of type 'LiteralControl ERROR

Whenever I try to write Following inside <select >   </select> I get error HtmlSelect' cannot have children of type 'LiteralControl 
  <optgroup label="Other Areas">
        <option value="Bihar" selected="selected">
        Bihar   
          </option>
      
        <option value="Bhopal">
        Bhopal
        </option>
       
        </optgroup>
      
 my complete code for select is :
<select id="city" runa ...