Which of the following does not contribute to the large surface area of the small intestine?

Most of the digestion and absorption of nutrients occur in the small intestine. Its length provides a large surface area for digestion and absorption, and that area is further increased by circular folds, villi, and microvilli. It is narrower (2.5 cm diameter) than the large intestine (6.5 cm diameter) but longer (3 m) than the large intestine (1.5 m).