The answer is B: cite several passages.
The tone or style that an author develops is a matter of taste, choice, and, above all, practice and perseverance, and as such, it is an ethereal element of his or her writing, which makes it very difficult —some would say, impossible— to imitate or replicate. So, in order to provide a sample of the author´s style or tone there is no better way to do it than to cite several passages so that the reader can form an idea for himself or herself of how such tone or style actually is. This also has the benefit of giving the reader the tools to go look for the citations in question to expand upon or corroborate his or her impressions that the essay provided.