The spinal cord is surrounded by bones (vertebrae), extends downward from the base.
I think it’s water vapor sorry if it’s wrong
What are the classifications of the animal kingdom?
According to the system set up by Linnaeus, all animals are classified into seven categories: kingdom, phylum, class, order, family, genus and species.
It is definitely not a primary source: this would be a book itself.
Now, is it a tertiary source? I don't think so: the author of the review should have read the book and should only be referring to this book in the review.
I think it's a secondary source.
Just find the similaritys and the differences