Ulna is the forearm bone involved in formation of elbow joint
Answer:
Explanation: Collenchyma cells are elongated cells with unevenly-thickened walls. They provide structural support, mainly to the stem and leaves.
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.
