What process allows radios to receive signals even when they are not in line of a tower?

a. Refraction

c. Diffraction

b. Reflection

d. Amplification

The answer is A. Refraction

Refraction is a change in direction of propagation of a wave due to a change in its transmission medium, by maintaining its frequency while changing the wave velocity at the same time will allows radios to receieve signals even though when they're not in line