线索法：1语意转折线索A formal letter is very different from an informal letter. Formal letters _1_ to businesses, schools or government offices. _2_ letters are for relatives, or former teachers. You may write an informal letter by hand, but you should _3_ a formal letter.1. A. send B. are written C. write D. are dropped2. A. Informal B. Formal C. Business D. Relative3. A. copy B. type C. write D. share 2因果关系线索It was a stra
