What key concept is indicated by the term "proton acceptors"?

The term "proton acceptors" is associated with bases in acid-base chemistry. A base is defined as a substance that can accept protons (H⁺ ions) from an acid. This is a fundamental concept in the Brønsted-Lowry acid-base theory, which categorizes substances based on their ability to donate or accept protons.

In this framework, when a base accepts a proton, it forms its conjugate acid. This behavior is essential in many chemical reactions and helps to explain how bases interact with acids. For example, when ammonia (NH₃) acts as a base, it accepts a proton to form ammonium (NH₄⁺).

Understanding this relationship between protons and bases is crucial for grasping broader concepts in chemistry, such as pH, buffering systems, and reaction dynamics. This is why the correct answer highlights the characteristics of bases as being proton acceptors.