Answer: DORSAL HOLLOW NERVE CORD.
The vertebrate spinal cord develops from the embryonic dorsal hollow nerve cord.
Explanation: The vertebrae spinal cord develops at around 6weeks to 7weeks gestational age once the neural tube closes,it develops from the embryonic dorsal hollow nerve cord,the plates folds forming the neural plate,the cranial end of the tube will form vessicles which are series of enlarged cavities,these vessicles will thereafter form the brain.
The spinal cord is made from part of the neural tube,the caudal end of this tube will form a narrower tube of almost same size along the same length that will eventually form the spinal cord.
