Answer
A; $32$ ft
Work Step by Step
We can assume the proportion between the height of the man and the length of the man's shadow is the same as it is for the length of the tree and the length of the tree's shadow. Therefore, if we find the proportion of the height of the man and the length of his shadow, we can find the height of the tree.
$6\times x=9$
$x=9\div6$
$x=1.5$
$y\times1.5=48$
$y=48\div1.5$
$y=32$
The height of the tree is 32 feet.