The potential energy U in joule of a particle of mass 1 kg moving in x-y plane obeys the law U = 4x + 3y, where (x, y) are the co-ordinates of the particle in metre. If the particle is at rest at (6, 4) at time t = 0, then:

A. coordinates of the particle at t = 1 sec are (4.5, 2)
B. The particle has constant acceleration
C. the speed of particle when it crosses the y-axis is 10 m/s
D. The particle has zero acceleration