Final answer:
Cylinder A undergoes isothermal expansion, where the temperature remains constant despite changes in volume and pressure.
Step-by-step explanation:
The type of expansion for Cylinder A is isothermal expansion. In an isothermal process, the temperature of the gas remains constant. Given that Cylinder A expands isothermally until the pressure drops to 1.0 atm, this indicates that although the volume is changing, the temperature is held constant at 350 K throughout the process. This can be contrasted with an adiabatic expansion, where no heat is transferred to or from the system and thus the temperature of the gas changes as a result of the expansion.