Pressure versus temperature graph of an ideal gas is as shown in figure.

Corresponding density ($\mathrm{\rho }$) versus volume (V) graph will be

Process AB is an isothermal process, i.e., $\mathrm{P}\propto 1/\mathrm{V}$ and since $\mathrm{\rho }\propto 1/\mathrm{V},\mathrm{\rho }-\mathrm{V}$ graph will be a rectangular hyperbola. 

Pressure is increasing; therefore, volume will increase. 

Process BC is an isochoric process. Therefore, V = constant and since $\mathrm{\rho }$ = m/V, density is also constant, i.e., $\mathrm{\rho }$ -V graph is a dot. Process CD is inverse of process AB and process DA is inverse is BC.