Consider a standing wave formed on a string . It results due to the superposition of two waves travelling in opposite directions . The waves are travelling along the length of the string in the `x` - direction and displacements of elements on the string are along the `y` - direction . Individual equations of the two waves can be expressed as `Y_(1) = 6 (cm) sin [ 5 (rad//cm) x - 4 ( rad//s)t]` `Y_(2) = 6(cm) sin [ 5 (rad//cm)x + 4 (rad//s)t]` Here `x` and `y` are in `cm`. Answer the following questions. Figure 7.104( c) shows the standing wave pattern at `t = 0` due to superposition of waves given by `y_(1)` and `y_(2)` in Figs.7.104(a) and (b) . In Fig. 7.104 (c ) , `N` is a node and `A` and antinode . At this instant say ` t = 0` , instantaneous velocity of points on the string A. is different for different pointsB. is zero for all pointsC. changes with position of the pointD. is constant but not equal to zero for all points