According to the Arrhenius theory, an acid is a substance that

which produces hydrogen ion in water, called acid. A substance which produces hydroxide ion in water, called base. According to Bronsted-Lowry theory, an acid is proton donor and base is proton acceptor. Actually, Arrhenius theory is limited only to the aqueous solution.

Explanation:

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.