A nonzero external force on a system of particles. The velocity and the acceleration of the cente of mass are found to be `v_0 and a_0` at an instant t. It is possible that
A. `v(0) = 0, a_(0) = 0`
B. `v(0) != 0, a_(0) = 0`
C. `v(0) = 0, a_(0) != 0`
D. `v(0) != 0, a_(0) != 0`