Correct answer choice is:
B. Be in phase with each other.
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Explanation:
Components waves mix to produce a resultant with the equivalent wavelength but the amplitude which is bigger than the amplitude of both of the unique component waves, and this results in constructive interference, which states that the interference of two or more waves of identical frequency and phase, constructing in their respective reinforcement and constructing a single amplitude equivalent to the total of the amplitudes of the unique waves.
