I keep getting B for some reason...

ABCD is a square with area 25.
now let side length be a.
hence a^2 = 25
ie a = 5.
Now, a= AD = 5.
Imagine drawing a line from O to X which is on AD and bisects it in half.
Now consider AOX triangle
here AX is 5/2 in length, since ABCD is a square , hence angle OAD will be 45 degrees.
Now OA cos 45 = AX. { understood right }
OA / sqrt ( 2 ) = 5/2
OA = 5 * sqrt (2) / 2

Area of the circle is pie radius^2.
radius is OA.
hence the overall area is = pie * 25 / 2