For versions of jQuery equal or above (>=) 1.6, use:
```JAVASCRIPT $("#option1").prop("checked", true); ```
For versions prior to (<) 1.6, use:
```JS $("#option1").attr('checked', 'checked'); ```
Tip: You may also want to call click() or change() on the radio button afterwards. See comments for more info.

For versions of jQuery equal or above (>=) 1.6, use:
$("#radio_1").prop("checked", true);
For versions prior to (<) 1.6, use:
$("#radio_1").attr('checked', 'checked'); **Tip:** You may also want to call `click()` or `change()` on the radio button afterwards. _See comments for more info._