Question

all the animals within the phylum chordata... possess a spinal cord. have some well - developed senses. have a well - developed brain. possess all these traits.

Explanation:

Chordates are defined by the presence of a notochord (which often develops into a spinal cord in vertebrates). While some chordates may have well - developed senses or brains (like vertebrates), not all do. For example, tunicates (a type of chordate) have a simple nervous system and no well - developed brain in the adult form. However, the defining characteristic of the phylum Chordata is the possession of a structure related to the spinal cord (derived from the notochord).

Answer:

A. possess a spinal cord.