Correct Answer: D

Rationale: The correct answer is D. Undigested food blocking the diverticulum can lead to bacterial invasion, causing inflammation and turning diverticulosis into diverticulitis. Choices A, B, and C do not directly facilitate the development of diverticulitis. Choice A involves a different mechanism related to laxative use, choice B describes a complication of chronic constipation but does not necessarily lead to diverticulitis, and choice C refers to a different condition involving herniation of the intestinal mucosa.

Correct Answer: D

Rationale: Crohn's disease can affect any part of the gastrointestinal tract from the mouth to the anus, but it commonly affects the small intestine and colon, involving the entire thickness of the bowel wall.

Correct Answer: C

Rationale: A gastroscopy is performed to visualize the stomach lining and obtain biopsies to diagnose gastric cancer.

Correct Answer: A

Rationale: Radiation therapy is used before surgery to reduce the size of the tumor, making it easier to remove.

Correct Answer: A

Rationale: Increasing fluid intake helps to enhance the effectiveness of colostomy irrigation by softening the stool and promoting better fecal return.