Seeing light coming out from a crack in the wall is what type of wave interaction? A. Reflection
B. Refraction
C. Diffraction
D. Resonance

C

becuase its where a wave (light etc) goes through a narrow area or across an edge of an area

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.