challenge: What is the primary function of Ipilimumab in relation to T lymphocytes and cancer cells?
  
  A. To turn off the inhibitory mechanism that interrupts T lymphocytes' destruction of cancer cells
  B. To stimulate the production of T lymphocytes to recognize and destroy cancer cells
  C. To enhance the inhibitory mechanism that prevents T lymphocytes from destroying cancer cells
  D. To directly destroy cancer cells by binding to them
  Answer: 