A. Tight junctions
B. Direct contact
Answer:- Tight junctions form a barrier to the passage of materials.
Tight junctions are cell junctions that are formed by the fusion of the outermost layers of plasma membranes of adjacent cells, creating a nearly impermeable barrier. Tight junctions are found in tissues that need to control the passage of molecules across the cell layer, such as the epithelium that lines the digestive tract, blood vessels, and other organs. They prevent the movement of ions and other molecules between cells, forcing them to move through the cells themselves, either by active transport or passive diffusion.
In contrast, direct contact, fat, and desmosomes do not form a barrier to the passage of materials. Desmosomes are anchoring junctions that bind cells together, but they do not regulate the passage of molecules between cells. Direct contact refers to physical contact between cells and does not involve the formation of a specific junction. Fat (adipose tissue) is a type of connective tissue that stores energy, but it does not have a role in regulating the passage of molecules between cells.