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

Increased surface area combined with close proximity of capillaries and lacteals to the epithelial surface.

Presence of multiple mucus-secreting goblet cells inside each villus which actively pump molecules across membranes.

High density of smooth muscle fibers within each villus to mechanically push nutrients into the blood.

A thick keratinized outer layer that prevents diffusion of pathogens at the cost of nutrient absorption.