Which of the following curves represent the variation of...

Volume expansion is the expansion of volume of a gas due to increase in its temperature. $\therefore$ Coefficient of volume expansion is given as $\alpha_{V}=\frac{\Delta V}{V \times \Delta T}...(i)$ where, $V=$ real volume of gas, $\Delta V$ - change in volume and $\Delta T=$ change in temperature. From idcal gas cquation, $p V=n R T \text{ or } T=\frac{p V}{n R}...(ii)$ For constant pressure, $$\begin{aligned} p \Delta V &=n R \Delta T \\ \frac{\Delta V}{\Delta T} &=\frac{n R}{p}...(iii) \end{aligned}$$ From Eqs. (i) and (iii), we get $\alpha_{V}=\frac{n R}{p V}=\frac{1}{T} \quad[\because \text{ From Eq. (ii) }]$ Thus, the variation of $\alpha_{V}$ with temperature is correctly depicted in option (b).