The correct option is D d-produce antibodies.
This diagram is about Areolar tissue in which A is Macrophages, B is Fibroblast, C is Collagen fibers, D is Mast cell. Macrophages are phagocytic in nature. Fibroblasts cells produce and secrete fibres. Collagen fibers provide strength and framework for epithelium. Mast cell serve as first line of defense against antigens entering the body due to their location in the skin and mucosa. But they do not produce antibodies.