Answer: HIV virus.
- A HIV virus
- B malaria parasite
- C typhoid bacterium
- D common cold virus
Correct answer: A. HIV virus
Explanation: AIDS is caused by the Human Immunodeficiency Virus (HIV).
The Plasmodium parasite needs both hosts: the female Anopheles mosquito injects sporozoites while biting (infecting the human liver and RBCs, causing the malaria fever cycle), then picks up gametocytes from an infected person's blood, completing the parasite's sexual stage inside the mosquito.
Concept context
Pathogens, infectious diseases, non-infectious diseases, drugs, cancer, and public health. High NEET importance.