option d.
as we know the corner of a square is always 90°. So we can apply that (side of the square)^2+(side of the square)^2 = (diagonal of the side)^2
(side of the square)^2+(side of the square)^2 = 16
16/2=8
8=(side of the square)^2
side of square= squareroot of 8
area of square= squareroot of 8^2=8
hence answer is 8
