The correct option is D A dorsal hollow nerve cord
A dorsal hollow nerve cord is a characteristic feature of a member of Chordata.
Scales are present in some chordates such as fishes, reptiles and birds. Others such as mammals do not have scales.
The members of Cyclostomata lack jaws. They are the most primitive chordates and belong to Agnatha (jawless).
Vertebrae are found only in vertebrates but not all chordates such as the urochordates and cephalochordates.