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  3. 　　Being a female tree is hard. A study of a species that can change sex has revealed that most striped maple trees die while fem

　　Being a female tree is hard. A study of a species that can change sex has revealed that most striped maple trees die while fem

admin2021-12-24  21
问题 　　Being a female tree is hard. A study of a species that can change sex has revealed that most striped maple trees die while female.
　　"We had a suspicion they were changing sex, which is relatively rare among plants." says Jemnifer Blake-Mahmud at Princeton University. Between 2014 and 2017, she and Lena Struwe at Rutgers University in New Jersey observed the life cycles of 457 striped maples in New Jersey, recording their health, diameter and whether they had female or male flowers each spring.
　　They found that 54 percent of the trees changed sex during that time, and one fourth of those did so at least twice. A model based on these findings showed that, contrary to previous suggestions, healthy trees were more likely to be male and a tree’s size doesn’t influence its sex.
　　The growth rate of trees that remained female for many years declined. Of the trees that died, 75 percent had recently produced female flowers. "It’s remarkable," says Blake-Mahmud. "When I see a tree that’s dead and I look back in my datasheet, it was almost always female the year before."
　　It isn’t clear why this is the case. It could be that female trees need more nutrients because they produce seeds, and it may increase the death rate of female trees, she says.
　　But it could also be that dying trees become female as a last effort to create offspring and pass their genes on to the next generation.
　　"These populations have a lot more male trees than female trees in general, so just by luck, a female has a better chance of being a parent of the next generation than a male," says Blake-Mahmud. "If you’re going to die anyway, then being female is the way to go. That would make more evolutionary sense."
Which factor mentioned in the passage does NOT influence the striped maple trees’ sex?
选项 A、Health.
B、Size.
C、Season.
D、Age.
答案B
解析 本题考查细节。根据题目中的influence可以定位到文中的第三段，“A model based on these findings showed that，contrary to previous suggestions，healthy trees were more likely to be male and a tree’s size doesn’t influence its sex．(这些发现表明，与前期的推测相反，健康的树木更有可能是雄性，而树的大小不会影响它的性别)”可以得知，答案为B。
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