Question

what do diffraction and refraction have in common?
they both involve interference.
they both involve wave interactions.
they both involve reflection.
they both involve construction.

Explanation:

Diffraction is the bending of waves around obstacles and openings. Refraction is the bending of waves when they enter a medium where their speed is different. Both diffraction and refraction are wave - related phenomena. Interference is a separate wave phenomenon (involving the superposition of waves). Reflection is the bouncing back of waves. Construction is not a relevant term in this context for these two wave behaviors.

Answer:

They both involve wave interactions.