The answer is D. Chordata.
There are three domains of life - Archaea, Bacteria, and Eukarya. All organisms that belong to the domains Archaea or Bacteria have cell walls. In the domain Eukarya, there are some groups that have cell walls and others that do not.
Chordata is phylum of the kingdom Animalia which belongs to the domain Eukarya. So, Chordata cannot be a domain.