A wave represented by the equation y = a cos (kx - ωt) is superimposed with another wave to form a stationary wave such that the point x = 0 is a node. The equation for other wave is
A. a sin (kx - ωt)
B. -a cos (kx - ωt)
C. -a cos (kx - ωt)
D. -a sin (kx - ωt)