Final answer:
A base reacts by accepting a proton, meaning it receives a hydrogen ion (H+), which is the true statement in accordance with the Brønsted-Lowry theory of acids and bases. The correct answer is option: a) It receives a hydrogen ion.
Step-by-step explanation:
When a base reacts with another substance, it functions by accepting a proton, according to the Brønsted-Lowry theory. The correct statement about a base in a reaction is that it receives a hydrogen ion (H+). This definition is broader than the Arrhenius definition, which solely defines bases as substances that produce hydroxide ions (OH-) in solution.
Furthermore, according to the Lewis theory, a base is regarded as an electron-pair donor, but in the context of this question, it is the Brønsted-Lowry definition that is relevant. Therefore, the base, in this case, does not donate a hydroxide ion; instead, it acts as a proton acceptor.