Answers for "dropdown selected value should be disable using html"

disable option dropdown jquery

//disable by value
$("#ddlList option[value='jquery']").attr("disabled","disabled");

//disable by text
$('#ddlList option:contains("HTML")').attr("disabled","disabled");

disable other options in select except the selected

$("#lbCountries").click(function () {
     $("#lbCountires option").each(function (index) {
        if ($(this).is(':selected')) {
            $(this).prop('disabled', false);
         }
         else {
            $(this).prop('disabled', true);
         }
      });
  });