单选题 When you have written a letter, read it through carefully; see that you have put in everything you intended, and have expressed it well; read it again, trying to put yourself in the place of the reader, to find'out what impression your letterwill make. The aim of the letter is to secure the interest of the reader, and his co -operation. The motto in letter- writing is: Remember the three C' s - Clear, Conciseness and Courtesy.