Final answer:
The Carnot cycle consists of two isothermal processes where the temperature remains constant and two adiabatic processes where no heat transfer occurs, making option (a) the correct answer.
Step-by-step explanation:
The Carnot cycle is a theoretical thermodynamic cycle that is composed of four reversible processes: two isothermal processes and two adiabatic processes. An isothermal process is one in which the temperature of the system remains constant, while in an adiabatic process, no heat transfer occurs into or out of the system.
The Carnot cycle is the most efficient cycle possible for a heat engine, setting an upper limit to the efficiency that real engines can achieve. The correct answer to the student's question is a) Isothermal and adiabatic processes.