The isothermal process on PV graph as shown below.
For isothermal process, the slope is
=− The adiabatic process on PV graph as shown below.
=− The isochoric process on PV graph as shown below.
For isochoric process, the slope is
=∞ The isobaric process on PV graph as shown below.
For isobaric process, the slope is
=0 Thus option (3) is correct.