The infective stage of Entamoeba histolytica is
Spore
Egg
Trophozoite
Cyst
As discussed in Protozoan Disease -
Entamoeba histolytica is a microscopic endoparasite of a man. It is usually found in the upper part of a large intestine. Its infection towards man depends upon the intake of food or water contaminated with fecal matter containing tetranucleate cyst of E.histolytica. Hence, the correct option is (d).