A rocket of mass 50 kg is fired vertically on the surface of earth. If velocity of exhaust gases relative to the rocket is 200 m/s and fuel is consumed at the rate of 4 kg/s, acceleration of the rocket is

• A

  0.8 $m/s^2$

• B

  1.5 $m/s^2$

• C

  4 $m/s^2$

• D

  6 $m/s^2$