The correct answer for this presented problem would be A. Article.
Articles are a kind of objective that gives more importance to the noun that it is used to describe and emphasize. As per this part of the sentence, there are currently 4 articles used. How much more when writing or delivering ordinary speeches, right? Articles are A and The, and sometimes An. Now, if the other options would outweigh articles, that would be impossible since articles are already an integral part of the English vocabulary to establish accuracy on both writing and speaking.