Abook review would be considered
a. a primary source.
b. a secondary source.
c. a tertiary source.
d. either a secondary or tertiary source, depending on content.

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.

Rna polymeras should attache to the promoter.