题目

如图，将半径为2 cm的圆形纸片折叠后，圆弧恰好经过圆心O，则折痕AB的长为( ) A . 2 cm B . cm C . D . 答案：C() 13. Her grandfather China for two years.   A. came          B. has come   C. has been in   D. has been to