AIDS is caused by HIV that principally infects

The correct option is D T-4 helper lymphocytes

• AIDS(acquired immunodeficiency syndrome) is caused by the HIV virus. It breaks down the body immune system, leaving the patient vulnerable to a host of life-threatening opportunistic infections.
  
• T-helper cells play an important role in adaptive immunity. They not only help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells.
• HIV destroys(CD4+ cells) T-helper lymphocytes cells.They're responsible for keeping you healthy from common diseases and infections. As HIV gradually weakens your natural defences, signs and symptoms will occur.
• Hence HIV attacks T-helper cells. Hence AIDS is caused by HIV that principally infects T-4 helper lymphocytes.
• So, the correct answer is 'T -4 helper lymphocytes'.