题目

.He is said________a book on the history of Chinese tone bridge , but I don’t know if he has finished it.   A. to have written   B. to be writing    C . having writing    D writing 答案：B等腰△ABC的一边BC的长为6，另外两边AB，AC的长分别是方程x2-8x+m=0的两个根，则m的值为    ．