In which process is work done on the system?

In the context of thermodynamics, the process in which work is done on the system is characterized by a change in the volume of the system under certain conditions. In an isobaric compression process, the pressure remains constant while the volume of the system decreases. As the volume decreases, the system must push against the external atmospheric pressure, which requires work to be done on the system to compress it.

Work can be represented mathematically in thermodynamics as the integral of pressure over the change in volume. In the case of isobaric compression, since the pressure is constant, the work done on the system can be calculated simply as the product of pressure and the change in volume. This results in positive work being added to the internal energy of the system.

Other processes mentioned, like isothermal expansion and adiabatic expansion, involve the system doing work on the surroundings. In isothermal compression, while work is also being done, the focus is on extracting work from the surroundings into the system, rather than work being done on the system itself. Hence, isobaric compression distinctly indicates that the system is receiving work, making it the correct answer.