The Huntington Library, located in San Marino, California, contains a significant collection of rare books and manuscripts. A visitor of the library will, in fact, find one of the original copies of the Gutenberg Bible, as well as first-edition copies of books by William Blake.
D. In fact is the correct answer choice to this question.
The other choices are either comparing or adding onto the idea. However, In fact is creating a strong statement to support the first sentence. It is phrased a bit weird, but it works, it would have made more snese if the question was:
In fact, a visitor of the library will find one of the original copies of the Gutenberg Bible, as well as first-edition copies of books by William Blake.
Hope this somewhat helped you and other readers out there also seeking the answer to this befuddling question. :3