wordpress show selected item

I am pulling certain pages using query_posts to populate a dropdown menu.

lets assume the list populate the following fields

option1, option2, option3 and option4

Now if I have selected option3 and my page changes to this, how do I display this as the selectedIndex?

<select name="speedC" id="speedC"
    onchange=开发者_如何学Go'document.location.href=this.options[this.selectedIndex].value;'> 
    <option value="">
    <?php echo attribute_escape(__('V&auml;lj en fr&aring;n listan')); ?></option> 
    <?php 
    $pages = get_pages('include=11,13,15,17,38'); 
    foreach ($pages as $pagg) {
        $option = '<option value="'.get_page_link($pagg->ID).'">';
        $option .= $pagg->post_title;
        $option .= '</option>';
       echo $option;
    } ?>
</select>

You want to use the Wordpress function is_page()

is_page('id')

Where 'id' is the id that you already have fetched. For more information, check the wordpress codex site

EDIT: I'm not too sure about the syntax here, but something like this might get you up and running:

<select name="speedC" id="speedC"
onchange='document.location.href=this.options[this.selectedIndex].value;'> 
<option value="">
<?php echo attribute_escape(__('V&auml;lj en fr&aring;n listan')); ?></option> 
<?php 
$pages = get_pages('include=11,13,15,17,38'); 
foreach ($pages as $pagg) {

    $option = '<option value="'.get_page_link($pagg->ID).'"';
    if(is_page($pagg->ID)){
       $option .= "SELECTED "
    }
    $option .= ">".$pagg->post_title;
    $option .= '</option>';
   echo $option;
} ?>
</select>