The correct answer is C. I bought a book, an atlas of famous caves.
Appositives and appositive phrases are used to describe subjects and direct objects. They are usually separated from the rest of the sentence using commas.
A is incorrect because the appositive a windbreaker is renaming the subject my jacket; B is incorrect because the appositive phrase a historic explorer is renaming the predicate nominative an archaeologist; D is incorrect because the appositive phrase the name of a famous operatic tenor is renaming object complement rather than the direct object.
This leaves us with sentence C - here, the noun a book is a direct object, and the appositive phrase an atlas of famous caves renames it.
