题目

—You should introduce yourself and start a conversation first. —______. You know I’m a shy person. A. Sorry to hear that B. You’re right C. I hope so  D. That sounds difficult 答案：D如图，将半径为4cm的圆形纸片折叠后，圆弧恰好经 过圆心O ，则折痕AB的长度为（     ） A.4 cm       B.cm     C.(2 +)cm     D. cm