题干

如图为高等动物生殖细胞正常分裂过程中,有关物质或结构数量变化的曲线,据图分析正确的是(    )

A:图中曲线可表示有丝分裂部分时期染色单体数目的变化

B:若细胞中发生了同源染色体联会,则该时期发生在图中的b点

C:若图中曲线表示有丝分裂过程中染色体组数目变化的部分曲线,则n=1

D:若图中曲线表示减数分裂过程中每条染色体上DNA分子数目变化的部分曲线,则n=1

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答案(点此获取答案解析)

D

同类题5

Teens Enjoy Reading
     According to a survey on reading conducted by the U.S. National Education Association (NEA), young Americans say reading is important—more important than computers and science. Over 50% of the twelve to eighteen years old children interviewed said they enjoy reading a lot. Seventy-nine percent find it stimulating and interesting, and 87% think it is relaxing. Most of those surveyed (68%) disagree with the opinion that reading is boring, or old-fashioned.
Teens Read Variety of Material
    Over half the teenagers interviewed said they read more than ten books a year. The results also showed that middle school students read more books than high school students. Most teens (66%) like to read fiction, such as novels and stories. Only 26% were interested in non-fiction, such as biographies and history books. Sixty-four percent of students liked reading ‘stories about people of my own age’ as their favorite topic. Mysteries and detective stories came second on the list at 53%. Just under 50% said they were interested in reading about their own culture and heritage.
Other Interests
    Of the teenagers who took part in the survey, 49% said that libraries are where they get most of their books. However, many complained that their school libraries do not have enough up-to-date, interesting books and magazines. Even though many teenagers in the U.S. enjoy reading, they still have other interests. When asked which activity would be the most difficult to give up for a week, 48% said listening to music. TV would be difficult to give up for 25% of those surveyed.
  ____
    Another survey which is published by www. SmartGirl.com studied the differences between teenage boys' and girls' reading habits. According to the report, more girls than boys read for fun. Many more girls (77%) than boys (6%) read fashion and beauty magazines. More boys (47%)  than girls (7%) read magazines about video games, but an equal number of each like to read adventure stories and newspapers. Girls also read more material about celebrities and social issues such as crime, drugs, or poverty. Boys, on the other hand, read more about sports.