Aca esta el codigo completo
Código HTML:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Prueba TABS</title>
<script language="javascript" type="text/javascript" src="./js/jquery.js"></script>
<script>
$(document).ready(function () {
$("#b1").click(function () {
selector = "#parhijo[0][pariente] option[value='HI']";
$(selector).attr("selected","selected");
});
});
</script>
</head>
<body>
<table id="tblacargo" name="tblacargo" class="tblacargo">
<tr>
<td><select name='parhijo[0][pariente]' id='parhijo[0][pariente]' class='parhijo[0][pariente]'>
<option selected='selected' value=''>Parentesco</option>
<option value='AB'>Abuelo/(a)</option>
<option value='HE'>HERMANO/(A)</option>
<option value='HI'>Hijo/(a)</option>
<option value='MA'>Madre</option>
<option value='PA'>Padre</option>
<option value='PR'>Primo/(a)</option>
<option value='SO'>Sobrino/(a)</option>
<option value='TI'>Tio/(a)</option>
</select>
</td>
</tr>
</table>
<input type="button" id="b1" name="b1" class="b1" value="Enviar">
</body>
</html>