Why would a letter from the author support his argument better than an essay

The brother of a presidential candidate writes an editorial in which he defends this candidate against charges of corruption. in such a circumstance, it is most appropriate for the reader to a) suspect that the candidate may have been framed. b) consider whether the candidate has the best family or not. c) wonder if the writer may be biased, due to his family connection. d) wonder if the writer may be inaccurate, due to wanting to get people to read his column. \