1 Exists

$meta_query = array(
	'relation' => 'AND',
	array(
		'key'     => 'ept',
		'compare' => 'NOT EXISTS',
	),
	array(
		'key'     => 'd0',
		'value'   => 'C D D',
		'compare' => '=',
		'type'    => 'CHAR',
	),
);