Acquired Immuno Deficiency Syndrome (AIDS) is caused by:

The correct answer is Option (3) → Virus

AIDS is caused by the Human Immunodeficiency Virus (HIV). The virus attacks the helper T-cells of the immune system, so the body slowly loses its power to fight infections, and illnesses that a healthy body would resist become serious.

HIV spreads through infected blood, unprotected sexual contact, shared needles and from an infected mother to her baby; it does not spread by touch or by sharing food.