Final answer:
The patient with ileitis, typically presenting as part of Crohn's disease, is most at risk for protein malabsorption, as inflammation of the ileum significantly disrupts nutrient uptake.
Step-by-step explanation:
The patient most at risk for malabsorption of protein is b. The patient with ileitis. Ileitis, an inflammation of the ileum, is often associated with Crohn's disease, which can affect any part of the gastrointestinal (GI) tract but most commonly affects the ileum. When the ileum is inflamed, it can impair the absorption of vital nutrients including proteins, leading to malnutrition and other related complications.