Immunology is the study of what?

Immunology is specifically the branch of biomedical science that focuses on the immune system and how it responds to pathogens, including bacteria, viruses, and other foreign elements that can cause disease. It encompasses the study of immunity, vaccine development, immune responses, and various related disorders.

Choosing "immunity to disease" acknowledges that immunology is fundamentally about understanding how organisms defend themselves against diseases and infections. This field includes the examination of both the innate and adaptive immune responses and explores mechanisms that protect the body from various health threats.

In contrast, the other options address areas outside the primary focus of immunology. For example, blood supply deficiencies relate more to hematology or vascular health, fecal matter falls under the study of gastroenterology or microbiology, and congenital disorders pertain to genetics and developmental biology rather than the immune system specifically.