In a P-V diagram (for an ideal gas), an isothermal curve will coincide withan adiabatic curve (through a point), when

Answer: Option B

The slope of isothermal process in $$p-v$$  plane is $$\frac{dP}{dV}=\frac{-P}{V}$$
The slope of adiabatic process in $$P-V$$  plane is $$\frac{dP}{dV}=-\gamma \frac{P}{V}$$
$$\Rightarrow$$ Slopes become equal when $$\gamma =1$$