I feel Option A is correct
We know from properties that square is a type of rectangle with all sides measuring equal in length
So, let us consider length of sides of rectangle = $a$
Now , in the given question, the length of 3 sides of rectangle is given = X
So we can rewrite it as , $X = 3a$
Now squaring on both sides , we get
$X^{^{2}} = 9a^{2}$
ie , $X^{^{2}}/9 = a^{2}$ ,
So , we know that area of square (We assume it as an equal side rectangle) = $a^{2}$
So the answer is Opt (A) = $X^{2}/9$