An ideal gas is undergoing a cyclic thermodynamic process in different ways as shown in the corresponding P - V diagrams in column 3 of the table. Consider only the path from state 1 to state $2 . \mathrm{W}$ denotes the corresponding work done on the system. The equations and plots in the table have standard notations as used in thermodynamic processes. Here $\gamma$ is the ratio of heat capacities at constant pressure and constant volume. The number of moles in the gas is $n$.

Which one of the following options correctly represents a thermodynamic process that is used as a correction in the determination of the speed of sound in an ideal gas ?