49. A mole of a monatomic ideal gas has pressure `P`, volume `V`, and temperature `T`. Which of the following processes would result in the greatest amount of energy added to the gas from heat?
(A) A process doubling the temperature at constant pressure.
(B) An adiabatic expansion doubling the volume.
(C) A process doubling the pressure at constant volume.
(D) A process doubling the volume at constant temperature.