Dear student,
There are three stages in the life cycle of the Amoeba, trophozoite, pre-cystic and the cystic stage. Tetranucleate cysts are eliminated in the faeces of the infected person. Infection with Entamoeba histolytica is acquired by indirect fecal-oral route or by sexual intercourse. The water or food which is contaminated with faeces is responsible for the entry of the cyst in the healthy individual. This cyst is the infective stage in the humans.
Thus, the correct answer is option D.
regards,
team Askiitians
