题目

--- The kind-hearted lady is popular with her neighbors, right? --- Yes. She is always ready to help others without expecting anything _______. A. in store                         B. in return                   C. in charge           D. in turn 答案：B若不等式ax2+5x+c＞0的解集为{x|13＜x＜12|}，则a+c的值为（　　）A．5B．-5C．7D．-7