Multiple categories

I have a front page with an overview of 2 categories, lets say fruits and vegetables:
<?php query_posts(‘category_name=fruits,vegetables&showposts=4’); ?>

When you ‘click read more’ you go to single.php. Part of the code there is:

<?php while ( have_posts() ) : the_post(); ?>
<?php
// Get the ID of a given category
$category_id = get_cat_ID( ‘Fruits’ );
// Get the URL of this category
$category_link = get_category_link( $category_id );
?>
<!– Print a link to this category –>
<p><a href="<?php echo esc_url( $category_link ); ?>" title="Go Back">? Go Back</a></p>

I can only put 1 category in this line of code $category_id = get_cat_ID( ‘Fruits’ );

Is it possible to have multiple categories? What I want is that when I click Go Back on fruits I will go back to an overview with only fruits; and when I click Go Back on vegetables I will go back to an overview with only vegetables?