A block A is placed over a long rough plank B of same mass as shown in figure. The plank is placed over a smooth horizontal surface. At time t = 0, block A is given a velocity${\text{v}}_{\text{0}}$ in horizontal direction. Let ${\text{v}}_{\text{1}}\text{and}{\text{v}}_{\text{2}}$ be the velocities of A and B at time t. Then choose the correct graph between ${\text{v}}_{\text{1}}\text{or}{\text{v}}_{\text{2}}$ and t :