A Rocket of Mass M Carries a Mass M of Fuel

A rocket of mass M carries a mass m of fuel and starts from rest. Which method of burning the fuel would result in the greatest final speed of the rocket after all the fuel is burned if the velocity of the exhaust gas relative to the rocket is fixed at u_ex?

A) Burn the exhaust gas at an exponentially increasing rate until it is exhausted.
B) Burn the fuel as slow as possible so the force on the rocket acts for the greatest time resulting in the greatest possible impulse to the rocket.
C) Burn the fuel slowly until the rocket reaches a speed equal to u_ex and then burn the remainder as quickly as possible so that the exhaust gas has the minimum kinetic energy.
D) Burn the exhaust gas at an exponentially decreasing rate to make it last forever.
E) Burn all the fuel in as short a time as possible.