Which of the following describes active immunity?

Active immunity refers to the protection that develops when a person's own immune system generates antibodies in response to an infection or vaccination. This type of immunity occurs when the body is exposed to a pathogen, such as bacteria or viruses, and responds by producing specific antibodies to combat the infection. Similarly, when vaccines are administered, they contain components that stimulate the immune system to produce its own antibodies without causing the disease, thereby providing lasting immunity.

The reason that this concept stands out in contrast to the other options is that while vaccines can indeed help in developing active immunity, they are not the only means—natural infections also contribute significantly to this type of immunity. The key factor here is the body’s active role in antibody production, which leads to long-lasting immunity, often for years or even a lifetime, depending on the disease and immune response.

Other options concerning immunity do not describe active immunity since they either refer to passive processes or provide temporary immunity. For instance, immunity from maternal antibodies is short-lived and does not involve the recipient's immune system producing its own antibodies.