Remove all options from Listbox empty()

Student
Tutorial on Listbox Enable Disable Listbox Select All options 
<script>
$(document).ready(function() {
$("#b1").click(function(){
$("#student").empty();
});
});
</script>
<?Php
echo "</div><div class='col-md-4'>";
require "templates/side_for_ad.php";
echo "</div></div>";
require "../../templates/temp1/analytic-only.php";
?>