①细胞的分化、衰老和癌变对于生物体都是有积极意义的 

②高度分化后的细胞遗传物质发生了改变 

③细胞的衰老与机体的衰老总是同步进行的 

④衰老细胞膜的通透性改变，有利于物质运输 

⑤有些病毒能诱发人的细胞癌变

⑥细胞癌变主要是因为原癌基因和抑癌基因发生突变

⑦癌细胞比正常细胞分裂周期长

    An officer（军官）is at a bus stop. He wants to see his girlfriend by bus. He wants to tell his girlfriend the time of his bus, and then she can meet him at the stop in her car. He wants to call his girlfriend on a pay phone（付费电话）,but he doesn't have a coin（硬币）for the phone. He wants someone to help him.

    A soldier（士兵）is near the stop. The officer walks to the soldier and asks,“Do you have any coins for the phone?”

    “Let me have a look,” says the soldier. “I'll see if I can help you.”

    “Don't you know how to speak to an officer?” says the officer. “Now let's say it. Do you have any coins for the phone?”

    “No, sir,” says the soldier.