题目

Have you ever heard the story of the four-minute mile? Many years ago, people believed that it was impossible for a human being to run a mile in less than four minutes until Roger Banister proved it wrong in1954. What happens if you put an animal in a pond? Any animal, big or small, will swim its way through. What happens when someone, who does not know how to swim, falls in deep waters? They drown. If an animal who has not learned swimming could escape by swimming, why not you? Because you believe you will drown while the animal does not. Have you ever wondered why the letters are organized i14．如图为人体细胞的分裂、分化、衰老和凋亡过程的示意图． ①～⑥为各个时期的细胞，a～c表示细胞所进行的生理过程，据此分析，下列有关说法正确的是（　　）A．细胞②与细胞①相比，相对表面积大，物质运输效率低B．细胞⑤与细胞⑥中的遗传物质不同C．细胞分化和衰老的过程均会改变细胞的形态、结构和功能D．胚胎发育过程中不发生细胞的凋亡