UPSEE Solved Model Paper 4

Given wave is = acos(kx−ωt)
a [cos kx cos ωt + sin kx sin ωt]
since we need node at X = 0 we need to cancel cos kx term in the um of given wave and superimposed wave
Hence superimposed wave is of form = - a cos [kx + ωt]
Hence (B) is correct answer.