reflection refraction diffraction absorption
I gave my students this multiple choice question: Sam looks into a fish pond and points at a goldfish. Sam's grandfather looks where Sam is pointing and tells Sam that the fish is actually in a different location. Which property of light explains why Sam's grandfather is correct?

Only one answer is correct among these 4 choices:
- reflection
- refraction
- diffraction
- absorption

Could you tell me which one is correct?

refraction