question: Q:A 37-year-old woman presents to the occupational health clinic for a new employee health screening. She has limited medical records prior to her immigration to the United States several years ago. She denies any current illness or significant medical history. Purified protein derivative (PPD) is injected on the inside of her left forearm for tuberculosis (TB) screening. Approximately 36 hours later, the patient comes back to the occupational health clinic and has an indurated lesion with bordering erythema measuring 15 mm in diameter at the site of PPD injection. Of the following options, which is the mechanism of her reaction?? 
  {'A': 'Type I–anaphylactic hypersensitivity reaction', 'B': 'Type II–cytotoxic hypersensitivity reaction', 'C': 'Type III–immune complex-mediated hypersensitivity reaction', 'D': 'Type IV–cell-mediated (delayed) hypersensitivity reaction', 'E': 'Type III and IV–mixed immune complex and cell-mediated hypersensitivity reactions'},