题目

Leonardo da Vinci (1452—1519) _______birds kept in cages in order to have the pleasure of setting them free. A. is said to be buying  B. is said to have bought     C. . had said to buy          D. has said to have bought   答案：B8．人体细胞中，具有双层膜的细胞器是（　　）①高尔基体         ②核膜         ③线粒体         ④叶绿体        ⑤内质网．A．③④B．②③④C．②③D．③