A salt is an ionic compound formed from the reaction of an acid and a base. This reaction is known as a neutralization reaction.

D.

A salt is an ionic compound formed from the reaction of an acid and a base. This reaction is known as a neutralization reaction.

• A. A compound that is always neutral: This is incorrect. While some salts are neutral, many can be acidic or basic depending on the strength of the acid and base from which they are formed.
• B. A mixture of acid and base: This is incorrect. A salt is a compound, not a mixture, and it is formed from an acid and a base, not a mixture of them.
• C. A substance formed from base only: This is incorrect. A salt is formed from both an acid and a base.
• D. A product of neutralization between an acid and a base: This is the most accurate definition. In a neutralization reaction, an acid reacts with a base to produce a salt and water.

The correct option is D.