The correct answer is C) The identification of HIV as the cause of AIDS.
Koch's postulates are a set of criteria used in microbiology to establish a causal relationship between a microorganism and a disease. These postulates are:
1. The microorganism must be present in individuals with the disease.
2. The microorganism must be isolated and grown in pure culture.
3. Inoculating a healthy individual with the pure culture should cause the same disease.
4. The microorganism must be reisolated from the newly infected individual.
In the case of HIV and AIDS, these postulates were followed to establish that HIV (Human Immunodeficiency Virus) is the cause of AIDS (Acquired Immunodeficiency Syndrome). HIV was identified as the virus present in individuals with AIDS, isolated, and shown to cause immunodeficiency when introduced into healthy individuals. The reisolation of HIV from those newly infected completed the postulates, providing strong evidence for its role in causing AIDS.