For which of the reactions is the net ionic equation: H^+ + OH^- ightarrow H2O?

Here are the solutions to the remaining questions:

23. For which of the reactions is the net ionic equation: $H^+ + OH^- \rightarrow H_2O$? This net ionic equation represents the neutralization of a strong acid by a strong soluble base.
    • (1) $HNO_3 + Mg(OH)_2 \rightarrow$ $HNO_3$ is a strong acid. $Mg(OH)_2$ is a strong base but sparingly soluble. The net ionic equation is $2H^+(aq) + Mg(OH)_2(s) \rightarrow Mg^{2+}(aq) + 2H_2O(l)$. This is not $H^+ + OH^- \rightarrow H_2O$.