The efficiency of a Carnot heat engine operating between absolute temperatures T1 and T2 (when, T1 > T2) is given by T_1 - T_2 T_1. The co-efficient of performance (C.O.P.) of a Carnot heat pump operating between T1 and T2 is given by

Answer: Option A

The efficiency of an heat engine is given by $$\stackrel{\iota }{\eta }=\frac{Q_1-Q_2}{Q_1}$$
For heat pump it is given by $$\stackrel{\iota }{\eta }=\frac{Q_1}{Q_1-Q_2}$$
Where $$Q_1$$ and $$Q_2$$ are given by heat taken and heat given to the thermal reservoirs respectively.
$$\Rightarrow {\left(\stackrel{\iota }{\eta }\right)}_{heatengine}=\frac{1}{{\left(\stackrel{\iota }{\eta }\right)}_{heatpump}}$$