题目

—Such a mistake could have been avoided.    —Unfortunately, he _______ the mistake again and again.    A．repeated       B. would repeat    C．had repeated        D. would have repeated 答案：A 解析: 由could have been avoided（本来可以避免）可知双方在谈论过去的事。故选A﹣15的相反数是（   ）A. 15 B. ﹣15 C. D. - A 【解析】根据只有符号不同的两个数互为相反数，可得﹣15的相反数是15， 故选：A．