Lithium nitrate and sodium nitrate, when heated separately, respectively, give :

$\mathrm{Li}_{2} \mathrm{O}, \mathrm{NaNO}_{2}$ <br/><br/> As per NCERT lithium nitrate when heated gives lithium oxide, $\mathrm{Li}_{2} \mathrm{O}$. Whereas other alkali metal nitrates decompose to give the corresponding nitrite. <br/><br/> $$4 \mathrm{LiNO}_{3} \longrightarrow 2 \mathrm{Li}_{2} \mathrm{O}+4 \mathrm{NO}_{2}+\mathrm{O}_{2}$$ <br/><br/> $2 \mathrm{NaNO}_{3} \longrightarrow 2 \mathrm{NaNO}_{2}+\mathrm{O}_{2}$ <br/><br/> However, the decomposition product of $\mathrm{NaNO}_{3}$ is temperature dependent process as shown in the below reaction.<br/><br/> $$\mathrm{NaNO}_{3} \underset{500^{\circ} \mathrm{C}}{\stackrel{\Delta}{\longrightarrow}} \mathrm{NaNO}_{2}(\mathrm{~s})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g})$$ <br/> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$\Delta \downarrow, 800^{\circ} \mathrm{C}$ <br/> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$$\mathrm{Na}_{2} \mathrm{O}(\mathrm{s})+\mathrm{N}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g})$$ <br/><br/> As the temperature is not mentioned, we can go by the answer. (C)