Most Animals with Backbones, Vertebrates, Have a Similar Body Plan

Most animals with backbones, vertebrates, have a similar body plan: skull, ribs, two pairs of limbs, tail. What does this suggest about vertebrates?

A) Vertebrates are the best designed organisms.
B) Vertebrates have been around longer than most other organisms.
C) Vertebrates all have similar lifestyles.
D) Vertebrates all adapted to similar environmental conditions.
E) Vertebrates are all related to a common ancestor.