The correct answer is B. He is using a very formal style
In writing, the style refers to the particular way in which a writer conveys a certain message that is determined by the words the writer uses. In the case of formal style, in this style, certain elements such as conventions of language and grammar, technical or complex words prevail while slangs, colloquial words or too informal words are avoided. This type of style can be identified in the text presented because the author of it avoid colloquial term or word and instead uses complex terms such as “legitimate standing in our language” or “Pei estimates that about 90 percent”. Therefore, in this case, the style can be mainly described as a very formal style.