Answer:
It provides a clear indication about Dr. Pascal's career.
Explanation:
Émile Zola's novel "Doctor Pascal" is from the Rougon-Macquart series, with it being the final novel of the series. The story revolves around themes of heredity and follows the protagonist Dr. Pascal and his life of practicing his profession.
In the given passage from the initial stage of the story, we are given the description of the room, Doctor Pascal's study. This room has cupboards and tables full of books, papers, etc. from his case studies and experiments from <em>"more than thirty years"</em> which include <em>"[his] great works on heredity."</em>
Thus, the use of this phrase gives the impression of how long or how vast the collection of papers was and thus, provides the immense 'proofs' of his career, Doctor Pascal's career. Through all these <em>"papers and manuscripts of all sorts, piled up in confusion and filling every shelf to overflowing"</em>, we are given an insight into what the doctor's career likely is.
Thus, the correct answer is the third option.
