-causes a severe form of gastroenteritis called giardiasis -discovered by Leeuwenhoek -can get if you drink water without boiling it first in the wild -has both live trophozoites and protective cysts -string test -teardrop shape with two eyes (nuclei) A. Giardia lamblia B. Entamoeba histolytica C. Cryptosporidium parvum D. Trichomonas vaginalis