I suck at geometry lol

Answer:
C
Step-by-step explanation:
Pythagorean theorem states that a^2 + b^2 = c^2. Let the length of the legs be x, so 2x^2 = c^2. c is the hypotenuse, which means that 2x^2 = 64. Divide both sides by 2, and we get x^2 = 32. Square root both sides and we get sqrt 32 or 4 * sqrt 2.