Which of the following compound is used for fixation of protozoa found in stool?

If immediate examination of stool is not possible, stool can be fixed by various fixatives. Poly vinyl alcohol (PVA) is most commonly used for preserving stool for protozoal examination. Fixed stool cannot be used for examining trophozoites. Eggs and cysts can survive the treatment of fixatives. Ref: Med Lab Tech Vol 2, 2nd ed by Kanai. L Mukherjee, Page 631, 808.