The correct answer is B, Strongyloides.  The rhabditiform larvae passed in stool can either molt twice and become infective (filariform) larvae (direct development) or molt four times and become free-living adult males and females which mate and produce rhabditiform larvae.  The latter in turn can either develop into new free-living adults, or into infective (filariforiform) larvae.  The filariform larvae penetrate the skin of the human host to initiate the parasitic cycle.  No intermediate host is involved in the life cycle of Strongyloides sp.

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