${z_1},{z_2}$ and ${z_3}$ as${z_1} = A\sin (kx - \omega \,t)$, ${z_2} = A\sin (kx + \omega \,t)$ and ${z_3} = A\sin (ky - \omega \,t)$.
Which of the following represents a standing wave

Which one of the following correctly shows the direction of the velocity of the points $1, 2$ and $3$ on the string