ADIABATIC process. But if entropy is not constant, then this process is called the polytropic process.Hint: This QUESTION can be solved by eliminating the options.Isothermal Process: An isothermal process is a process in which TEMPERATURE remains constant. i.e. T1 = T2 ⇒ ΔU = 0For the isothermal process δQ = -δW ≠ 0Isentropic Process: ΔS = 0Hyperbolic Process is the isothermal processSo the process cannot be isothermal/hyperbolic and ISENTROPIC. It can only be polytropic.