What is the output of the following code? <code> 1 <?php 2 $a = ‘a’; $b = &#821

What is the output of the following code?
<code>
1 <?php
2 $a = ‘a’; $b = ‘b’;
3 echo isset($c) ? $a.$b.$c : ($c = ‘c’).’d’;
4 ?>
</code>

A.
abc

B.
cd

C.
0d