题目

Book three is ______ most difficult book,but is isn’t ______ most difficult one in Senior school books. A.a;aB.a;theC.the;theD.the;a 答案：B计算（﹣9）﹣（﹣3）的结果是（　　）A. ﹣12 B. ﹣6 C. +6 D. 12