Redness, swelling, pain and heat are classical signs of acute inflammation. Inflammation is a tissue reaction to infection or injury. Mast cells are found in tissues and they appear to be the key players in the initiation of inflammation. It is responsible for bringing various other cells to the site of infection. Histamine is released from the granules of mast cells and are released from the mast cells by exocytosis, which increases the blood flow to the area. Thus, the quick release of histamine produces redness and swelling due to inflammation. Prostaglandins are another potent mediators of inflammation and produces these symptoms.Thus, the correct answer is option A.