The energy at a point due to the sound wave is proportional to the square of the pressure amplitude. When two waves with the same frequency and constant phase difference interfere, the energy is redistributed because the resultant pressure amplitude p₀ is given by p₀² = p₀₁² + p₀₂²+ 2p₀¹ p₀² cosδ here p₀¹ and p₀² are pressure amplitudes of the two waves and δ is the phase difference. Since δ is constant here, so p₀ remains constant in time. Thus the energy redistribution remains constant in time. So the option D is correct.