A block A of mass m is placed over a plank B of mass 2m. Plank B is placed over a smooth horizontal surface. The coefficient of friction between A and B is `(1)/(2)` block A is given a velocity `v_(0)` towards right. Accelration of B relative to A is
A. `(g)/(2)`
B. zero
C. `(3g)/(4)`
D. `(g)/(4)`
