The correct option is B Pharynx with gill slits
Pharyngeal gill slits are present in both chordates as well as hemichordates.
Chordates show presence of solid, rod like structure on the dorsal side called notochord in atleast some part of their lifecycle. All chordates have at some stage of life, gill slites on the lateral sides of the pharynx.
Hemichordates do not show presence of notochord. They have gill slits present but are dorsal in position.