A disease that breaks down the body's immune system.

• A. AIDS
• B. HIV
• C. Hepatitis B
• D. Flu

Answer: (A)

AIDS represents a severe weakening of the immune system, making it hard for the body to fight infections and diseases. It stands for Acquired Immunodeficiency Syndrome and is the stage reached when immune cells (CD4 T cells) are so diminished that opportunistic infections and certain cancers can take hold. HIV is the virus that attacks the immune system and can lead to AIDS if not treated, but AIDS itself is the condition characterized by immune system failure. Hepatitis B mainly affects the liver, not the immune system, and the flu is an acute respiratory illness that doesn’t cause lasting immune deficiency. So the description of a disease that breaks down the body's immune system best points to AIDS.