question: Q:A group of investigators is performing a phase I trial of a novel drug among patients with chronic right upper quadrant pain. Iminodiacetic acid labeled with technetium 99m is administered intravenously and subjects are subsequently imaged with a gamma camera. It is found that administration of the experimental drug increases the amount of iminodiacetic acid in the intestines. The effect of this novel drug is most similar to that of a substance secreted by which of the following cells?? 
  {'A': 'Duodenal K cells', 'B': 'Pancreatic D cells', 'C': 'Antral G cells', 'D': 'Duodenal S cells', 'E': 'Jejunal I cells'},