What is the output of the following code?

What is the output of the following code?
<code>
$a = 3;
switch($a) {
case1: echo ‘one’; break;
case2: echo ‘two’; break;
default: echo ‘four’; break;
case3: echo ‘three’; break;
}
</code>

A.
one

B.
two

C.
three

D.
four