题干

下列关于细胞及其生命历程的说法正确的是(  )

A:人、动物体的遗传物质在致癌因子作用下突变为原癌基因和抑癌基因

B:细胞分化使多细胞生物中的细胞功能趋向全面化,提高细胞代谢的效率

C:细胞衰老最终表现为细胞的形态、结构、功能和遗传物质均发生变化

D:细胞凋亡受遗传物质的严格控制,并且在凋亡的过程中存在基因表达

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D

同类题4

阅读理解

B

    In choosing a friend, one should be very careful. A good friend can help you study. You can have fun together and make each other happy. Sometimes you will meet fair-weather friends. They will be with you only if you have money or luck, but when you are down, they will run away. How do I know when I have found a good friend? I look for certain qualities of characteristic, especially understanding, honesty and reliability (可靠).

    Above all else, I look for understanding in a friend. A good friend tries to understand how another person is feeling. He is not quick to give his opinion. Instead, he tries to learn from others. He puts himself in the other person's place, and he tries to think of ways to be helpful. He is also a good listener.

    At the same time, however, a good friend is honest. He does not look for faults (过错) in others. He notices their good points. In short, a friend will try to understand me and accept me.

    Another quality of a friend is reliability. I can always depend on (信赖) a good friend. If he tells me he will meet me somewhere at a certain time, I can be sure that he will be there. If I need help, he will do his best to help me. If I am in trouble, he will not run away from me.

    There is a fourth quality that makes a friend special. A special friend is someone with whom we can have fun. We should enjoy our lives, and we would enjoy our friendship. That is why I especially like friends who are fun to be with. A good friend likes the same things I like. We share experience (经验) and learn from each other. A good friend has a good sense of humour, too. He likes to laugh with me. That is how we share in the joy of being friends. And I know that he is looking for the same quality in me.

    When I meet someone who is reliable, honest, and understanding, I know I've found a friend!