Answer: The correct answer is "Light or sound waves change direction"
Explanation:
Refraction: Refraction occurs when a light rays gets bend while travelling from one medium to the another medium due to change in the speed of light or change in the direction. From the given options, the best definition of refraction is "Light or sound waves change direction".
Reflection: Reflection occurs when the light rays get reflected back from the obstacle in a same medium without getting absorb or transmit in it.
From the given options, the best definition of reflection is "Light or sound wave bounce off a medium.
Therefore, the correct option is (A).