For several years, Corey has suffered from intermittent abdominal pain along with bouts of diarrhea and constipation. According to Corey, his bad guts worsen whenever he is stressed out or eats certain foods, especially raw fruit and baked beans. His doctor has determined that his intestinal tract is not inflamed. Based on this information, Corey probably has ________.
a) Irritable bowel syndrome (IBS)
b) Crohn's disease
c) Celiac disease
d) Gastritis