<prompt> Neurulation is completed on day:141821None of the above  <response>: Closure of the cranial neuropore occurs at approximately day 25 18- to 20-somite stage, whereas the posterior neuropore closes at day 28 25-somite stage. Neurulation is then complete, and the central nervous system is represented by a closed tubular structure with a narrow caudal poion, the spinal cord, and a much broader cephalic poion characterized by a number of dilations, the brain vesicles Ref: Langmans embryology 11th edition Chapter 5. 