Which of the following describes a process of conferring immunity by injecting an antigen?

Immunization refers to the process of stimulating the immune system to develop a specific defense against a pathogen by introducing an antigen. When an antigen is injected into the body, it triggers an immune response that includes the production of antibodies. This prepares the immune system to recognize and combat the pathogen if it is encountered again in the future, effectively conferring immunity.

In contrast, diagnosis involves identifying a disease or condition rather than providing immunity. Antiviral therapy specifically targets viruses, often by inhibiting their replication but does not introduce antigens to confer immunity. Antibacterial treatment focuses on attacking bacteria, typically through the use of antibiotics, without creating an immune response correlated with an antigen. Thus, the correct answer highlights the fundamental aspect of immunity development through the introduction of antigens, which is at the core of immunization.