JS / AJAX：隐藏/显示选择框

The function disables select boxes that do not match with the main category. I have one main category and two subcategories. Is there a way i can hide and show the subcategories select boxes instead of disabling them?

JS/AJAX

<script type="text/javascript">
var formObject = {
    run : function(obj) {

            obj.nextAll('.update').html('<option value="">----</option>').attr('disabled', true);
            var id = obj.attr('id');
            var v = obj.val();
            jQuery.getJSON('update.php', { id : id, value : v }, function(data) {
                if (!data.error) {
                    obj.next('.update').html(data.list).removeAttr('disabled');
                } else {
                    obj.nextAll('.update').html('<option value="">----</option>').attr('disabled', true);
                }
            });
        }   
}; 
</script>

You can use the style='display:none;' attribute. Or using JQuery, $("#subc1").show() / $("#subc2").hide().