∆U=nCv∆T For isothermal process T is constant So ∆U=0 A⟶II Adiabatic process ∆Q=0 ∆Q=∆U+∆W ∆U=−∆W Work done by gas is positive So ∆U is negative B ⟶ I For Isochoric process ∆W=0 C⟶IV For Isobaric process ∆W=P∆V≠0 ∆U=nCV∆T≠0 Heat absorbed goes partly to increase internal energy and partly do work.