<select ng-model="et.edate" ng-options="et.edate as et.edate for et in endTimeArr" ng-change="getET(et.edate)" class="ng-pristine ng-untouched ng-valid">

<option value="?" selected="selected"></option>

<option value="string:2016-07-07 21:00" label="2016-07-07 21:00">2016-07-021:00</option>            

<option value="string:2016-07-07 21:30" label="2016-07-07 21:30">2016-07-07 21:30</option>

</select>

请问<option value="?" selected="selected"></option> 这个是怎么出来的 如何去掉呢？