The correct option is A Entamoeba histolytica
Entamoeba histolytica is a protozoan that causes amoebic dysentery. The symptoms include mild stomach pains, frequent elimination of stool or diarrhea are the primary symptoms of dysentery. It is transmitted by food and water contaminated by fecal matter. Housefly may act as a vector for the disease. Thus, the correct answer is option A.