question: Q:Three days after starting a new drug for malaria prophylaxis, a 19-year-old college student comes to the physician because of dark-colored urine and fatigue. He has not had any fever, dysuria, or abdominal pain. He has no history of serious illness. Physical examination shows scleral icterus. Laboratory studies show a hemoglobin of 9.7 g/dL and serum lactate dehydrogenase of 234 U/L. Peripheral blood smear shows poikilocytes with bite-shaped irregularities. Which of the following drugs has the patient most likely been taking?? 
  {'A': 'Pyrimethamine', 'B': 'Primaquine', 'C': 'Dapsone', 'D': 'Ivermectin', 'E': 'Doxycycline'},