Explanation:

- Option 1: Frog

- Frogs are amphibians.

- They have a backbone, which is part of their vertebrate structure.

- Option 2: Human

- Humans are mammals.

- They definitely have a backbone, essential for their body structure.

- Option 3: Spider

- Spiders are arachnids, not vertebrates.

- They do not have a backbone. They have an exoskeleton.

- Option 4: Pigeon

- Pigeons are birds.

- Like all birds, they have a backbone.

The correct answer is Option 3: Spider.

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