In the following reactions, ZnO is respectively acting as a/an : $(a) ZnO+Na_2 O → Na_2ZnO_2 \\ (b) ZnO+CO_2 → ZnCO_3$

Question

$\begin{array}{1 1} \text{(1) acid and acid} \\ \text{(2) acid and base} \\ \text{(3) base and acid} \\ \text{(4) base and base } \end{array} $