chosen-change-add-empty-option
HTML
<script src="//cdnjs.cloudflare.com/ajax/libs/chosen/1.1.0/chosen.jquery.min.js"></script>
<link rel="stylesheet" href="http://cdnjs.cloudflare.com/ajax/libs/chosen/1.1.0/chosen.min.css">
<select id="chosen-without-empty" class="yalgauda">
<option value="2">example</option>
<option value="3">example 2</option>
</select>
<br />
JavaScript
$('.yalgauda').chosen({
width: '50%',
allow_single_deselect: false
});