If a wave hits a smooth surface at an angle of incidence of 40 degrees, the angle of reflection is

A. 0 degrees.

B. 40 degrees.

C. 90 degrees.

D. 80 degrees.

So we want to know what is the angle of reflection of the wave if the incident angle is 40 degrees. So when the incident wave hits a surface under some angle, the reflecting angle should be the same as the angle of incidence. So the correct answer is B. 40 degrees.