Answer:
According to the proton theory of acids and bases by J. Brønsted and T. Lowry, the acid is proton donor.
Step-by-step explanation:
According to the Bronsted lowry concept an acid is substance that gives protons or hydrogen ion while,
Base is substance that accept hydrogen ion or proton.
Consider the following example:
NH₃ + HCl → NH₄⁺ + Cl⁻
In this example HCl is Bronsted lowry acid it gives H⁺ while ammonia is Bronsted lowry base because it accept H⁺.
This also gives the concept of conjugate acid and base. In given example Cl⁻ is conjugate base of HCl while NH₄⁺ is conjugate acid of ammonia.