Select the reagents that reduce nitriles to primary amines : A. (i)...

Nitriles ($R-CN$) can be reduced to primary amines ($R-CH_2NH_2$) using strong reducing agents or catalytic hydrogenation.

Reagent A: $\text{LiAlH}_4$ followed by hydrolysis is a strong reducing agent that reduces nitriles to primary amines.

Reagent C: $\text{H}_2/\text{Ni}$ (catalytic hydrogenation) reduces nitriles to primary amines.

Reagent D: $\text{Na(Hg)}/\text{C}_2\text{H}_5\text{OH}$ (Mendius reduction) provides nascent hydrogen and reduces nitriles to primary amines.

Reagent B: $\text{Sn} + \text{HCl}$ is typically used to reduce nitro compounds to amines. (Note: $\text{SnCl}_2 + \text{HCl}$ is used in Stephen reduction to convert nitriles to aldehydes).

Reagent E: $\text{Br}_2/\text{aq. NaOH}$ is used for Hoffmann bromamide degradation to convert amides to primary amines, not nitriles.

Thus, A, C, and D are the correct reagents.

Answer: A, C and D only