Which immunity is developed through the injection of antigens that stimulate the body's immune system?

The correct response pertains to active immunity, which is developed through the injection of antigens that stimulate the body’s immune system to produce its own antibodies. This process often occurs through vaccinations. When a vaccine is administered, it introduces a harmless part of the pathogen (the antigen) to the immune system. The body responds by creating specific antibodies that offer protection against future infections by the real pathogen.

In contrast, passive immunity is achieved when antibodies are transferred from one individual to another, such as through maternal antibodies passed to an infant via breast milk. This type of immunity provides immediate protection but does not involve the recipient's immune system actively producing antibodies, hence it is temporary.

Natural immunity arises from direct exposure to infectious agents, leading to the development of antibodies as the immune system responds to the infection without external intervention. Acquired immunity refers more broadly to immunity gained either through active or passive means, but it doesn't specifically capture the process of vaccination which directly prompts the immune response. Thus, the specific and correct understanding of how antigens stimulate the immune response is central to recognizing the characteristics of active immunity, making it the appropriate answer.