The correct answer is C, collect specimens in 10% formalin; perform a FEA, modified acid-fast stain, and chromotrope 2R (Weber) stain; examine the acid-fast slide and the chromotrope 2R slide.  PVA fixative is not necessary for these two parasites and cannot be used to examine either Cryptosporidium or microsporidia.  The FEA done on the formalin specimen would be used to prepare the acid-fast slide to be examined for Cryptosporidium and may be used to prepare the chromotrope 2R slide to be examined for microsporidia.  FEA is optional for microsporidia; concentration neither increases nor decreases these parasites, but it will reduce background.  The added advantage of having FEA material is that a direct fluorescent antibody assay can also be performed if desired.