I've one select dropdown control in HTML as follows :

```
<select id="student" name="student" class="form-control"></select>

```

I want to call a jQuery-AJAX function which will add the option values to the above HTML select control. 

Following is the code for I've written for it:

```
    $.ajax({
      url : "http://google.com",
      cache: false,
      dataType: "json",
      type: "GET",
      async: false,
      data: {
        'request_type':'ajax', 
        'op':'get_all_students'
      },
      success: function(result, success) { 
        $('#student').html(result);
      },
      error: function() {
        alert("Error is occured");
      }
    });

```

My issue is on which event of HTML select dropdown should I call the above jQuery-AJAX function in order to add the option values dynamically?

Please suggest me the proper way to do this.