Final answer:
The cell type that secretes histamine at the site of an infection is the mast cell. Macrophages are both phagocytic and can produce chemicals that promote inflammation. Among the choice given, macrophages are the cells that are phagocytic.
Step-by-step explanation:
The cell type that secretes histamine at the site of an infection is the mast cell (C). Mast cells play a critical role in the inflammatory process. They are found in connective tissues and mucosal environments and are responsible for releasing histamines and other chemicals during inflammatory and allergic reactions.
Macrophages (A) are immune cells that can both phagocytize pathogens and produce chemicals that promote inflammation, making them a dual threat in the immune response. Also, within the context of antigen presentation, macrophages, along with dendritic cells and B cells, are involved in stimulating T cells to release cytokines which enhance the phagocytic activity and help in the immune response.
The phagocytic cells among the options are macrophages (B). Macrophages engulf and digest cellular debris and pathogens, playing a significant role in both innate and adaptive immunity.