How to set the selected attribute on a dropdown box.

How to set the selected attribute on a dropdown box.

Let say I have the following HTML.
  1. <select id="gt_pref_bl">
      <option value='enabled'>Enabled</option>
      <option value='disabled' selected>Disabled</option>
    </select>



Now what I am trying to do is if the person clicks the Enabled option. I want it to changed the option to be selected.

Any ideas? I am going to store this value also.