Question

multiple choice question
vertebrates are distinguished by the presence of a
exoskeleton made of bone.
dorsal nerve cord.
vertebral column, or backbone.
postanal tail.

Explanation:

Vertebrates are animals that have a vertebral column or backbone. An exoskeleton made of bone is not a characteristic of vertebrates. While a dorsal nerve cord and a postanal tail are features of chordates (of which vertebrates are a part), the specific distinguishing feature for vertebrates among the options is the vertebral column.

Answer:

vertebral column, or backbone.