Final answer:
Entamoeba histolytica is a protozoan parasite found in feces that causes amoebiasis and is transmitted through feces-contaminated food or water.
Step-by-step explanation:
The protozoan parasite Entamoeba histolytica is the causative agent of amoebiasis, and it is known to be transmitted through consumption of food or water contaminated with feces. Regarding the body fluid in which Entamoeba histolytica is found, it is most commonly present in D) Feces. This is because E. histolytica forms cysts that are passed in the feces of infected persons and can survive outside the body, leading to potential contamination of water and food sources. When a person ingests cyst-contaminated water or food, they can develop the infection which might lead to symptoms ranging from nonexistent to severe amoebic dysentery.