Reversible expansion of an ideal gas under isothermal and adiabatic...

From first law of thermodynamics, $\Delta$\mathrm{U}=\mathrm{q}$+\mathrm{W}$In adiabatic expansion, $q=0$ \therefore \quad $\Delta \mathrm{U}=\mathrm{W}$During expansion of a gas $w$ is negative i.e $w \lt 0$ or $\Delta \mathrm{U} \lt 0$. We know that, $\Delta$\mathrm{U}=\mathrm{nC}$_{\mathrm{V}} \Delta \mathrm{T}$ $$\begin{array}{lclc} \therefore& \mathrm{nC}_{\mathrm{V}} \Delta \mathrm{T}< 0 & \text{ or }& \Delta \mathrm{T}< 0 \\ \therefore & \mathrm{T}_{\mathrm{C}}-\mathrm{T}_{\mathrm{A}}< 0 & \text{ or }& \mathrm{T}_{\mathrm{C}}< \mathrm{T}_{\mathrm{A}} \end{array}$$Thus, option (4) is incorrect while the remaining options are correct.