$\mathrm{NH}_3+\mathrm{HCl}$ (2:1 mole ratio)

$\mathrm{CH}_3 \mathrm{CO}_2 \mathrm{H}+\mathrm{NaOH}$ ( $2: 1$ mole ratio)

$\mathrm{NaOH}+\mathrm{CH}_3 \mathrm{COOH}$ (1:1 mole ratio)

$\mathrm{NH}_4 \mathrm{Cl}+\mathrm{NH}_3$ (1:1 mole ratio)

$A$ and $R$ are true and $R$ is the correct explanation of $A$.

$A$ and $R$ are true, but $R$ is not the correct explanation for $A$.

$A$ is true but $R$ is false.

A is false but $R$ is true.

electron pair donor

electron pair acceptor

proton donor

proton acceptor