Answer:
Option a. Adiabatic
Explanation:
Adiabatic system is one in which there is no exchange of mass and heat in between the system and its surrounding and the only transfer is in the form of work done.
In this process the internal energy of the system depends on the temperature and increases with the increase in temperature and as there is no exchange of heat between surrounding and system temperature as well as internal energy of the thermodynamic system increases.
Therefore, the work done not only compresses the gas but it is utilized in raising system's internal energy.
Thus, it is in adiabatic process that results in most work done on the gas.