How to deselect last selected option from Listbox using jQuery in ASP.Net

I want to deselect last selected option from listbox if he select maximum 8 options from listbox.if he select next ninth option then there should be alert like below in code and automatic deselect that ninth option.

<script>
    $(document).ready(function () {
        $("#SelectedIndustryList")
          .change(function () {

              var sel = [];
              $("#SelectedIndustryList option:selected").each(function () {
                  //str += $(this).text() + " ";
                  var count = $("#SelectedIndustryList option:selected").length;
                  if (count > 8) {
                      //var selectedItem = $("#SelectedIndustryList option:selected").index();


                      $('#lbl_msg').html("You can select only maximum 8 Industries.");
                      $('#msgBox').show();
                     



                  }

              });

          })
          .trigger("change");
    });
</script>