html select onchange事件

<select name="CluefromType" id="CluefromType" style="width: 182px" onchange="return CluefromOtherTypeSelected();">
       <option value="市场走访">
        市场走访
       </option>
       <option value="工厂走访">
        工厂走访
       </option>
       <option value="展会">
        展会
       </option>
       <option value="线人">
        线人
       </option>
       <option value="调查公司">
        调查公司
       </option>
       <option value="其他">
        其他
       </option>
      </select>
  function CluefromOtherTypeSelected(){
                  if   (document.all["CluefromType"].selectedIndex   ==  "5")   {
                     document.getElementById("CluefromOtherType").style.display="";  
                  }
                   if   (document.all["Clue