Which of the following is a characteristic of vertebrates

A vertebrate is an animal with a spinal cord surrounded by cartilage or bone. The word comes from vertebrae, the bones that make up the spine. Animals that are not vertebrates are called invertebrates. Vertebrates include birds, fish, amphibians, reptiles, and mammals.

Vertebrate Characteristics

General characteristics of the sub-phylum Vertebrata are as follows: 
Vertebrates have a well developed brain.Brain is set inside a bony box, known as cranium.Notochord is present in all chordates during sometime of development, it is formed on the dorsal side of the primitive gut in the early embryo stage.Most vertebrates possess guts with a non-terminal anus. The mouth cavity and the oesophagus is connected by the pharyngeal gill slits to a muscular tube pharynx, which opens to the exterior.They possess a dorsal hollow nerve tube at some stage of their life. Possess a dorsal cartilaginous nerve rod known as the notochord. At some stage of their life possess gill slits in the pharyngeal region.Have partially open circulatory system.Possess two pairs of appendages.The endoskeleton is made of cartilage or bone.The first vertebrates were jawless fishes with single caudal fin.The advancement of vertebrates with a hinged jaw which opened new food options and jawed fishes became the dominant creatures in the sea.All vertebrates have a heart and closed circulatory system.Reproduction is normally sexual.Feed on variety of organic materials.Unisexual animals, have one pair of gonads.

This is the most closely resembles the model.