This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
Causative agent of AIDS was discovered in - 
Select and explain. 
A. 1983, B. 1976, C. 1969, D. 1992
A: 1983
Answer: A: 1983 
Explanation: Ans. is 'a' i.e., 1983 * In 1983, human immunodeficiency virus (HIV) was isolated from a patient with lymphadenopathy, and by 1984 it was demonstrated clearly to be the causative agent of AIDS.