Thanks for this !
I use that and problem is solved !
<?php
// vars
$place = get_field('lieu');
// check
if( $place && in_array('maintenon', $place) ): ?>
<span class="label label-primary labellieu">Château de Maintenon</span>
<?php elseif( $place && in_array('archives', $place) ):?>
<span class="label label label-warning labellieu">Archives départementales</span>
<?php elseif( $place && in_array('compa', $place) ):?>
<span class="label label label-danger labellieu">Le Compa</span>
<?php elseif( $place && in_array('classe', $place) ):?>
<span class="label label-success labellieu">Dans la classe</span>
<?php endif; ?>
