Answer: Option A
:
C
Let us analyse each process separately. BC is an isothermal process, which implies that the P-Cgraph would be represented by a rectangular hyperbola. (Since PV= constant).
This rectangular hyperbola starts at a lower volume $V_1$ and goes to a higher volume as represented in the figure below -

Process AB is an isochoric process, which in a P-Vgraph would be a vertical line. Also we notice that the temperature drops in this process, whichimplies that the pressure will also drop (since PV=nRT, when Vis constant $P\propto T$). Therefore point Acan be anywhere on the line represented in blue in the figure below.

Process C - A
This process is an isobaric process since it represents a curve where $V\propto T$ (this is possible only when pressure is a constant, remember Charles' law?). So the process can be represented by a horizontal line in a P-Vgraph. The point where the line joining process A-Band C-Ameet is the point A.