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

上一题 下一题 0.0难度 选择题 更新时间:2014-12-05 02:28:46

答案(点此获取答案解析)

D

同类题3

阅读理解

    Here comes a story that many years ago a man arrived at a village in India to catch monkeys so he could sell them to zoos. The monkeys, however, were very clever and every sort of trap he set failed. A young boy watched the man's pathetic efforts and laughed.

    The man said, “If you can catch me a monkey, I'll give you $ 2.” That was a huge amount of money then.

    The boy went to his home and took a clay pot with a narrow neck. He placed a few nuts around the pot and put lots of nuts inside. He then tied the pot to a tree and told the man, “We should have a rest in a few hours. Let's wait in the village. The monkey will call us when he is ready.”

    Certainly enough, a band of monkeys soon discovered the nuts and the pot. One slipped his hand in the pot and grabbed a handful of nuts, but he couldn't pull his hand out of the narrow opening of the pot because his fist(拳头) was clenched. The monkey feared and started making loud noises. Some of the other monkeys tried unsuccessfully to pull the pot off his hand.

    The boy and the man heard the noises and the boy got a big strong bag. As they approached the monkeys they all ran away except the one with its hand in the pot. The boy grabbed the monkey and the pot. The man was amazed and asked the boy the secret of his monkey trap, “Why was it so easy for the monkey to get his hand in but so hard to get it out?”

    The boy laughed and said, “The monkey could have easily got his hand back out and escaped, but he would have had to let go of the nuts in the pot and he just wasn't willing to let go. They never are.”

    What lessons can be learned from this story? Do people sometimes trap themselves by holding onto things that they should let go? Do you?

根据短文内容,选择最佳答案,并将选定答案的字母标号填在题前括号内。