Đáp án đúng: C
NaCl.
$\begin{array}{l}N{{a}_{2}}O\,(1\,mol)\,\xrightarrow{{}}\,NaOH\,(2\,mol)\\NH_{4}^{+}\,+\,O{{H}^{-}}\,\xrightarrow{{}}\,N{{H}_{3}}\,+\,{{H}_{2}}O\\1\,mol\,\,\,\,1\,mol\\HCO_{3}^{-}\,+\,O{{H}^{-}}\,\xrightarrow{{}}\,CO_{3}^{2-}\,+\,{{H}_{2}}O\\1\,mol\,\,\,\,\,\,1\,mol\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,1\,mol\\B{{a}^{2+}}\,+\,CO_{3}^{2-}\,\xrightarrow{{}}\,BaC{{O}_{3}}\\1\,mol\,\,\,\,1\,mol\end{array}$