Q.The V-T diagram of an ideal gas which goes through a reversible cycle $A\to B\to C\to D$ is shown below (a closed loop on a $V$-$T$ graph with the four states labelled $A$, $B$, $C$, $D$ in order). (Processes $D\to A$ and $B\to C$ are adiabatic.) The corresponding PV diagram for the process is (all figures are schematic): four alternative small P-V sketches are offered, each redrawing the same four states $A,B,C,D$ with a different combination of straight/curved connecting segments, labelled a) b) c) d) -- the actual shape of each of the four option sketches is not legible in the extracted source.