Which of the following is characteristic of bases?

The correct choice highlights a fundamental property of bases in the context of acid-base chemistry. Bases are substances that can either release hydroxide ions (OH⁻) when dissolved in water or accept hydrogen ions (H⁺) from acids. This dual behavior is key in defining substances as bases.

For instance, when a substance like sodium hydroxide (NaOH) is dissolved, it dissociates to produce hydroxide ions, which makes the solution basic. Alternatively, when a base accepts hydrogen ions, it effectively neutralizes acids, which is another crucial part of its functionality in chemical reactions.

In contrast, substances described in other choices do not embody the characteristics of bases: a pH less than 7 indicates acidity, the release of hydrogen ions points to acidic behavior, and being always neutral refers to substances that do not exhibit either acidic or basic qualities, such as water. Thus, choice C provides the most accurate and comprehensive characterization of bases in terms of their chemical behavior.