How to replace ComboBox values on a button click?

How to replace ComboBox values on a button click?

I have a button and I want to replace the elements of the combobox.

  2.   <select id="combobox">
  3.     <option value="">Select an option</option>
  4.     <option value="opa">OpA</option>
  5.     <option value="opb">OpBt</option>
  6.     <option value="opc">OpC</option>
  7.   </select>
I want when a user clicks on the button, the elements of combBox changes to a retrieved data from my database.

For instance, change all:

 <option value="opa">OpA</option>
  <option value="opb">OpBt</option>
  <option value="opc">OpC</option>
to:

 <option value="IT">IT</option>
  <option value="Accounting">Accounting</option>
  <option value="HR">HR</option>
I tried .html() but it is not going well.

  2.       function loaddata() {
  3.                   $.ajax({
  4.                       type: "POST",
  5.                       contentType: "application/json; charset=utf-8",
  6.                       url: "WebService.asmx/GetData",
  7.                       data: "{}",
  8.                       dataType: "json",
  9.                       success: function (data) {
  10.                           response(data.d);
  11.                           $("#comboox").html();

  13.                       },
  14.                       error: function (result) {
  15.                           alert(result);
  16.                       }
  17.                   });
  18.               }