Which description best matches AIDS?

• A. The early stage of HIV where the immune system is healthy.
• B. The late stage of HIV where the immune system is fully damaged and vulnerable to diseases and death.
• C. A vaccine to prevent HIV.
• D. A liver infection not related to HIV.

Answer: (B)

AIDS is the advanced stage of HIV infection when the immune system is severely weakened. HIV attacks CD4 T cells, which are crucial for coordinating the body's defense against infections. As these cells drop to very low levels or when certain serious infections (opportunistic infections) or cancers occur, the body becomes vulnerable to illnesses that a healthy immune system could usually prevent. That combination of a greatly compromised immune system and increased risk of serious infections or death is what defines AIDS. The other descriptions don’t capture this extreme immune failure or the associated health risks, so they don’t fit as well.