Answer:
Diffraction
Step-by-step explanation:
When light enters water at an angle, it is bent downward by diffraction. However, our brain sees the underwater image as if it were on a straight line.
Thus, the bottom of the pool appears to be shallower than it actually is.
A is wrong. If all the light were reflected from the surface, we wouldn't be able to see the person's feet.
B is wrong. if all the light rays interfered with each other, we wouldn't be able to see anything.
D is wrong. Refraction is the bending of light as it passes the edge of an object.