All chordates have (at some point in their life cycle). feathers diaphragm fins pharyngeal pouches

The correct answer is pharyngeal pouches.

   All chordates for at least some period of their life have pharyngeal pouches (pharyngeal slits). Those are the openings in the pharynx with the function in the filter-feeding. Pharyngeal slits are present during the embryonic stages of tetrapod development. They develop into gill arches  (bony fish) and into the jaw and inner ear (terrestrial animals).

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The answer would be c