On which triangle can the law of cosines be applied once to find an unknown angle measure? Law of cosines: a2 = b2 + c2 – 2bccos(A)

Triangle X W Y is shown. Angle X Y W is a right angle. The length of hypotenuse W X is y, the length of X Y is a, and the length of W Y is 9.
Triangle W X Y is shown. Sides W X and X Y are congruent. The length of W Y is 7.
Triangle W X Y is shown. Angle X Y W is 76 degrees. The length of X Y is 5, the length of W Y is 10, and the length of W X is y.
Triangle W X Y is shown. The length of W X is 10, the length of X Y is 8, and the length of W Y is 16.

Idek Know where to began but I do not think that C is correct