I like Jorge Luis Borges' essay 'The Wall and the Books,' but I like his book Collected Fictions better.

What do you think?

I think It's C

Not C.

http://guidetogrammar.org/grammar/italics.htm#titles

The word or phrase in the sentence that needs to be in italics is C. 'The Wall and the Books.'

To format text in italics, you typically use quotation marks or single quotation marks. In this case, 'The Wall and the Books' is a book title, so it should be italicized to indicate it as a specific work.