Given a scientific question, generate a correct answer to it.

[EX Q]: Vertebrates. from the smallest of fish to us. one of the main features we all have in common is our what?
[EX A]: backbone

[EX Q]: Reef sponges typically have what type of beneficial relationships with other reef species?
[EX A]: symbiotic

[EX Q]: Ionic compounds contain cations and anions rather than what?
[EX A]:
discrete neutral molecules