This may also be useful, so I thought I'd add it here.
If you would like to select a value based on the item's value and not the index of that item then you can do the following:
Your select list:
The jquery:
$('#selectBox option[value=C]').attr('selected', 'selected');
$('#selectBox option[value=C]').prop('selected', true);
The selected item would be "Number 2" now.