What is the main characteristic of a buffer solution?

A buffer solution is defined primarily by its ability to resist changes in pH when small amounts of acids or bases are added. This property is crucial in many biological and chemical systems where maintaining a stable pH is necessary for proper functioning. Buffers typically consist of a weak acid and its conjugate base or a weak base and its conjugate acid, which work together to neutralize added acids or bases without causing significant shifts in pH.

When an acid (proton donor) is added to a buffer, the weak base component of the buffer reacts with the excess protons, thereby minimizing the change in pH. Conversely, if a base (proton acceptor) is added, the weak acid component of the buffer can donate protons to counteract the increase in pH. This equilibrium action is what makes buffers so effective in maintaining pH stability.

In contrast to the other provided choices, the key characteristic of resistance to pH changes is what defines a buffer. The options suggesting dramatic pH changes or the necessity of only using strong acids and bases do not embody the true essence of a buffer's functionality. Additionally, the notion that a buffer eliminates all acids and bases present is inaccurate, as it instead maintains a balance among them.