Q. What kind of reagent would  be needed to resolve a racemic amine, such as 2-aminobutane ?

1. the pure optically active amine to serve as a template for crystallization
2. an achiral carboxylic acid to give a racemic mixture of amine salts.
3. An enantiomerically pure chiral carboxylic acid to give a diastereomeric mixture of amine salts.
4. A racemic chiral carboxylic acid to give a complete mixture of isomeric amine salts.