Work done in time t on a body of mass m which is accelerated from rest to a speed v in time t₁, as a function of time t, is given by:

A. 1/2 mv (t/t1)
B. 1/2 mv (mv/t¹)² t²
C. m (v/t₁) t²
D. (1/2) m(v²/t²1) t²