题目

Not a single mistake _____ in the dictation yesterday. A. did he make      B. made by him     C. he made     D. he had made 答案：A12．在?ABCD中，对角线AC与BD相交于点O，如果△OBC的周长是59，且AD的长是28，两对角线之差是14，试分别求出两条对角线的长．