Answer
a) Stage 1
b) Stage 3
c) Stage 3
d) Stage 2
Work Step by Step
a) As we see in the given graph, stage 1 is an isochoric process in which the volume is constant but the temperature increases.
So, the heat is added to this stage.
b) As we see in the given graph, stage 3 is an isobaric process in which the pressure is constant but the temperature decreases.
So, the heat is removed in this stage.
c) As we see in the given graph, stage 3 is an isobaric process in which the pressure is constant and the volume of the gas is compressed which means that there is work done on the gas.
So, the work done on the gas is in this stage.
d) As we see in the given graph, stage 2 is an isothermal process in which the temperature is constant and the volume of the gas is expanded which means that there is work done by the gas.
So, the work done by the gas is in this stage.