Problem: A 25-year-old female presents with gastrointestinal problems that occur especially with stress. She is in graduate school and notices that when she is getting ready for an exam, she has severe stomach cramps and abdominal bloating that is relieved by defecation. These symptoms have occurred about 4 days a month for the last 5 months. She also experiences a decrease in appetite and has alternating diarrhea and constipation. The patient denies any sick contacts, recent travel, change in diet, or change in medications. Which of the following diagnostic modalities can confirm the suspected diagnosis? A. Colonoscopy B. Hydrogen breath testing C. Rome IV criteria D. Tissue transglutaminase antibody testing