As per the rules of binomial nomenclature, which species name is written correctly?

A) pelecinus polyturator

B) Pelecinus polyturator

C) Pelecinus polyturator

As per the rules of bionomial nomenclature, the species name that is written correctly is C. Pelecinus polytyrator (or B, because you wrote two answers which are completely the same).

You capitalize the genus name, but write the specific epithet in small letters.