Answer: I would contend that the right answer is the A) It emphasizes the influence of slang.
Explanation: Just to elaborate a little on the answer, it can be added that by writing that <em>even</em> the great Shakespeare used slang words the author is emphasizing the influence of this way of speaking, since not only more contemporary and less influential individuals, but also Shakespeare employed it. Option C can be discarded, since the sentence actually confirms Shakespeare's influence on language, and option D can also be discarded, since it is irrelevant—the short word "even" does not lengthen the sentence. One could think that using "even" might suggest that the author wants to contrast Shakespare's reputation for more formal words with his use of slang, but the use of the adjective "beautiful" is not accurate (the author is not describing slang in negative terms), so this option should be eliminated as well.
