A. which of the four thermal processes describes the pressure-volume relationship at a constant temperature?

The thermal process that occurs when pressure and volume are variable, while the temperature remains constant is known as an isothermal process. Due to the change in temperature being zero, the internal energy of the system does not change. Isothermal processes can be carried out adiabatically or non-adiabatically. (An adiabatic process is where the heat energy moving through the boundary of a system is 0)