Efficient absorption in the small intestine requires a very large surface area, which is provided by several structural modifications of the small intestine. Match each structure with its proper description.

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Large folds of the mucosa and submucosa

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Small projections of the mucosa

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Microscopic folds of the cell membrane on the free surface of each columnar cell

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Also called the brush border
A. Plica circulares
B. Villi
C. Microvilli