The correct answer is B, modified Kinyoun’s acid-fast stain.  This is the staining technique of choice for identification of Cryptosporidium sp.  Safranin staining (especially hot stain) is also suitable for detection of this coccidian parasite.  Cryptosporidium sp. oocysts do not stain consistently with Gram stain.  Methylene blue stain does not stain Cryptosporidium sp. oocysts, but is used in the Sabin-Feldman dye test, a method used to diagnose toxoplasmosis.