Which structural feature of villi most increases the efficiency of nutrient absorption?

• A. Increased surface area combined with close proximity of capillaries and lacteals to the epithelial surface.
• B. Presence of multiple mucus-secreting goblet cells inside each villus which actively pump molecules across membranes.
• C. High density of smooth muscle fibers within each villus to mechanically push nutrients into the blood.
• D. A thick keratinized outer layer that prevents diffusion of pathogens at the cost of nutrient absorption.

Answer: (A)