You will be given a definition of a task first, then some input of the task.
Given a scientific passage and an answer, generate a question for the given answer.

Passage: Vertebrates. From the smallest of fish to us. One of the main features we all have in common is our backbone. Vertebrates describes main biological features of fish, amphibians, reptiles, birds, and mammals. Answer: backbone
Output:
Vertebrates. from the smallest of fish to us. one of the main features we all have in common is our what?