question: Q:A 14-year-old boy presents to his pediatrician with a 5-day history of abdominal pain and bloody stool. He denies having a fever and says that he has not experienced any other symptoms associated with the abdominal pain. He has no past medical history and does not take any medications or supplements. His family history is significant for a grandfather who developed Alzheimer disease at age 80 and a cousin who died at age 21 from colon cancer. Physical exam is unremarkable. Based on clinical suspicion a colonoscopy is obtained showing hundreds of small polyps in the colon. A mutation of a gene on which of the following chromosomes is most likely responsible for this patient's symptoms?? 
  {'A': '5', 'B': '7', 'C': '17', 'D': '19', 'E': 'X'},