4. What affects the size of an angle? A. Its location B. The amount of rotation of one side C. The length of its sides D. The number of degrees in its supplement

The correct answer is

D. The number of degrees in its supplement

The size of the sides and the rotation is irrelevant and would still keep the angle having the same size. The number of degrees in the supplement decides how big an angle is because the larger the supplementary angle the smaller the angle we're observing will be, and vice versa.