The reflected ray will have an angle of 56 degrees, or answer C. This is because the angle of incident and the reflected ray’s angles will add to 90 degrees. The easiest way to find the angle of the reflected ray, it follows, is to subtract the angle of incidence from 90. Likewise, if this question had been asking you to find the ray of incidence with a reflected ray of 56 degrees, you could do the same thing to find the ray of incidence.

There is not a lot of information available to those who are not incredibly good at math that can be easily understood about why the angle of incidence and the reflected angle come to 90 degrees total. However, for those in math, it would make sense.