The correct answer is C, the clip demonstrates the excystation of the C. parvum sporozoite from an oocyst.  After ingestion by a suitable host, excystation occurs and the sporozoites are released to parasitize epithelial cells of the intestinal mucosa.  A mature oocyst of Cryptosporidium sp. contains 4 sporozoites which are not enclosed in a sporocyst, different from other intestinal coccidian genera, e.g., Cyclopora, Isospora, Eimeria.

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