Final answer:
The transport of amino acids across epithelial membranes requires facilitated diffusion.D. facilitated diffusion.
Step-by-step explanation:
The transport of amino acids across epithelial membranes requires facilitated diffusion. Facilitated diffusion is a type of passive transport that uses specific carrier proteins in the cell membrane to move substances from an area of higher concentration to an area of lower concentration. In this case, carrier proteins help move amino acids from outside the cell to inside the cell.