They all have fur. They all have backbones. They all are warm-blooded. They all have young that look like the adults.
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: What do all vertebrate animals have in common?
Possibilities:
- They all have fur.
- They all have backbones.
- They all are warm-blooded.
- They all have young that look like the adults.

They all have backbones.