A wave `y = a sin (omegat - kx)` on a string meets with another wave producing a node at `x = 0`. Then the equation of the unknown wave is
A. `y = a sin(omega t + kx)`
B. `y = -a sin(omega t +kx)`
C. `y = a sin (omega t - kx)`
D. `y = -a sin (omega t - kx)`
