Which types of cell junctions are needed in a mucosal membrane, such as the digestive tract, to keep the digestive enzymes, juices, and bacteria from leaking out?

The correct answer is tight junctions.  

Tight junctions are found mainly in the epithelial cells like an intestinal brush border. Water and other fluids must be inhibited from crossing or sipping between the neighboring cells, so that the fluids do not slowly goes across the intestinal lining.  

Tight junctions seal adjacent epithelial cells in a narrow band just within their apical surface. They comprise of an alignment of claudins and other proteins. One of their essential function is to restrict the movement of ions and molecules via the space between the cells.  

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i think that d. wind is the answer.   i missed the question when i answered a. currents.