题干

如图是干细胞发育过程中的三个途径,下列说法正确的是(  )

A:人的造血干细胞可以分化为多种细胞

B:干细胞分化使细胞的数量和种类越来越多

C:组织细胞的衰老受基因调控,但细胞的结构不发生改变

D:组织细胞的凋亡不利于个体发育,但细胞内溶酶体的功能增强

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答案(点此获取答案解析)

A

同类题3

    There is a famous English saying "You are what you eat", and it means what you put in your mouth will become part of you. Many experts(专家) use it to tell people it's important to have a good eating habit. For example, too much sweet food makes a person overweight. To avoid being fat, kids are told to keep off sweet food. However, a team of American scientists have discovered something new about eating sweet food.
"When we say some people 'sweet', we mean they are kind and friendly to us. Perhaps this word can help us learn more about people's feelings and acts." said Brian Meier, a scientist from the study team. "Taste is something we experience every day. What we have done is to find whether we can know someone's character and behavior depending on their taste."
    In one of their experiments, college students were asked questions about their character- whether, for example, they were soft-hearted or not. Then they were asked to make a list of their favorite food. According to their answers, the scientists found that the students who liked sweet  food were nicer.
    In their another experiment, the scientists found that people who preferred sweet food such as cookies and chocolate were more willing to help other people in need, and those who ate non-sweet food such as chips weren't. For example, people with a sweet tooth were more likely to volunteer to clean up their city, visit sick children in the hospital and so on.
    The result of the experiments is that people's helpfulness or being nice has something to do with their taste for sweet food. So eating sweet food is a useful way to make people nice and helpful. Next time, try some ice-cream.