Correct Answer: C

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

Correct Answer: B

Rationale: In the early stages of peritonitis, the client would exhibit abdominal pain and rigidity due to inflammation.

Correct Answer: C

Rationale: Clients with gastric cancer may experience a feeling of fullness due to the presence of the tumor.

Correct Answer: A

Rationale: The priority focus of nursing management for a client with peritonitis is fluid and electrolyte balance to prevent shock.

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.