Correct option (a) AIDS
Explanation :
AIDS or acquired immunodeficiency syndrome or acquired immune deficiency syndrome (a death warrant) is a serious disease (also called slim disease) caused by a retrovirus HIV (human immunodeficiency virus). It is a set of symptoms and infections resulting from the damage to the human immune system by the virus, that depletes primarily the number of T-lymphocytes (CD-4 T-cells or helper T-cells) and renders the patient susceptible to opportunistic infections i.e, infection caused by non-pathogens.