Which of the following substances can act as an acid according to the Bronsted-Lowry theory?

According to the Bronsted-Lowry theory of acids and bases, an acid is defined as a substance that donates protons (H⁺ ions) to another substance in a chemical reaction. This definition emphasizes the role of protons in acid-base chemistry, distinguishing it from other theories that may focus on hydrogen ion presence in the solution or the substances' ability to turn litmus paper red.

When a substance donates a proton, it effectively increases the concentration of H⁺ ions in the solution, which is a characteristic behavior of acids. Therefore, understanding that the donating of protons is the fundamental action of acids within this theory helps to clarify the functionalities and interactions of various chemical substances in acid-base reactions.

The options that involve accepting protons, being neutral, or simply being described as a basic solution do not align with the definition of an acid in the Bronsted-Lowry framework, as they pertain to bases or do not engage in proton transfer at all.