What will be the output of the following PHP code?

 <?php  $a = array(A, Cat, Dog, A, Dog);
print_r(array_count_values($a));
?> 

A.

Array ( [A] => 2 [Cat] => 1 [Dog] => 2 )

B.

Array ( [A] => 2 [Cat] => 2 [Dog] => 1 )

C.

Array ( [A] => 1 [Cat] => 1 [Dog] => 2 )

D.

Array ( [A] => 2 [Cat] => 1 [Dog] => 1)