Answer: The correct answer is- B. The stomach is no longer secreting pepsin.
Pepsin is a protein digesting enzyme, which is produced in the stomach to convert proteins into small peptides. In other words, it performs protein digestion in the stomach.
As per the information in the question, a doctor hypothesizes that a patient's digestive system is not properly secreting digestive enzymes.
Bile is secreted by liver for the digestion of lipids in small intestine whereas pancreas secrete pancreatic juice containing various enzymes for food digestion in small intestine.
Thus, out of the given options, B) is the most plausible diagnosis.