Chordates have A. Dorsal nerve cordB. Dorsal hollow nerve cordC. BrainD. Ventral nerve cord

The correct answer is B. Dorsal hollow nerve cord.

Explanation:

Chordates are a group of animals that possess certain key characteristics at some stage in their development. These include:

Dorsal nerve cord: Chordates have a nerve cord that runs along their back. In most chordates, this nerve cord is hollow (hence the term "dorsal hollow nerve cord"). This is a defining feature of the phylum Chordata.

Brain: While chordates do have a brain, it is not a unique characteristic that defines the entire group. The presence of a brain comes from the development of the dorsal nerve cord into the brain in vertebrates.

Ventral nerve cord: This is found in invertebrates like arthropods, not in chordates. In chordates, the nerve cord is located dorsally (on the back side of the body).

Thus, the most accurate and defining feature of chordates is the dorsal hollow nerve cord (option B).