Multiple Selectable solution

Multiple Selectable solution

Hay, anyone can help my problem. I have 2 selectable like this :
<ul id="selectable1" class="selectable-continue ui-selectable">
 <li>select1</li>
 <li>select2</li>
</ul>
<ul id="selectable2" class="selectable-continue ui-selectable">
 <li>select3</li>
 <li>select4</li>
</ul>
<script language="javascript">
 $(document).ready(function(){
  $('.selectable-continue').selectable();
 });
</script>
why they can sparate selected, i make that class selectable .
So when select1 selected and go to select3 selected, 2 selectable can selected. T_T, i don't why ??