Question

Which characteristic is unique to vertebrates?

A) they all have a well-defined skeleton

B) they have no defined organ systems

C) they have bilateral symmetry

D) they have an exoskeleton
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Answer 1

Answer is A)They have a well-defined skeleton

Step-by-step explanation:

most reasonable answer

Answer 2

Answer: They have well-defined skeleton.

Step-by-step explanation:

This is because the vertebrates are uniquely characterised by the presence of the bones.