A square ABCD is inscribed in a quarter circle where B is on the circumference of the circle and D is the center of the circle. The length of diagonal AC of the square, if the circle's radius is 5, is

A

$$\frac{5\pi}{4}$$

B

$$\frac{5\pi}{2}$$

C

5

D

$$5\sqrt{2}$$

E

The length cannot be determined.