A particle moving in the xy plane experiences a velocity dependent force `vec F = k (v_yhati + v_x hat j)`, where `v_x and v_y` are the x and y components of its velocity `vec v` . If `vec a` is the acceleration of the particle, then which of the following statements is true for the particle?

Options

A. quantity `vec v xx vec a` is constant in time
B. `vec F` arises due to a magnetic field
C. kinetic energy of particle is constant in time
D. quantity `vec v. vec a` is constant in time