题目

As you know, it is my duty to ________ my younger sisters from being hurt when they are in danger. A. prevent        B. save           C. stop         D. protect 答案：D  与植物细胞相比，动物细胞不具有的结构是（　　）A．细胞膜B．细胞质C．细胞壁D．细胞核