Which statement best describes the superposition principle?

A.) If two in-phase waves arrive simultaneously at a point, their amplitudes add up.

B.) If two out-of-phase waves arrive simultaneously at a point, there amplitudes add up.

C.) If two in-phase waves arrive at a point one after another, their amplitudes add up.

D.) If two out-of-face waves arrive at a point one after the other, their amplitudes add up.