Let's look at the sentences you wrote:
- Original: "It is small and has a spiky back."
- Check: This sentence is correct. It tells us about something that is small and has spikes on its back.
- Original: "It curls up in a ball not to become a snack."
- Check: This sentence is almost right, but it's missing a small word called a comma before "not" to help it sound better. It should be: "It curls up in a ball, not to become a snack." This means the animal rolls up tightly so other animals don't eat it.
Great job! Remember, when you have extra information like "not to become a snack," it’s good to use a comma before it to make the sentence easier to understand.