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In the digestive system, Vitamin B12 bound to intrinsic factor (B12-IF) is absorbed through the epithelium of the small intestine and delivered into the extracellular fluid on the basolateral membrane of the epithelium by a process called transcytosis. This process begins on the apical surface of the epithelial cell when the B12-IF binds to receptors, and is engulfed into the cell. What is the type of membrane transport at the apical surface of the epithelium?