In a polytropic process, the term $\left [ \left ( \frac{\gamma -n}{\gamma -1} \right )\left ( \frac{p_{1}V_{1}-p_{2}V_{2}}{n-1} \right ) \right ]$ is equal to
(a) Heat absorbed or rejected
(b) Change in internal energy
(c) Ratio of T1/T2
(d) Work done during polytropic expansion