题干

某校老师发现,在做叶绿体中色素的提取和分离的实验时,若采用沸水冲烫菠菜叶约15s,再按常规研磨液萃取的方法,得到的色素提取液更浓更绿。其主要原因是

A:沸水冲烫菠菜叶引起脱水,色素被浓缩

B:沸水冲烫菠菜叶使研磨充分,色素完全释放

C:分解色素的酶失活,色素损失少

D:菠菜叶的色素耐高温而不耐低温

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答案(点此获取答案解析)

C

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    Knowing how much her own children loved presents at Christmas, Ann Sutton always tried to seek help for one or two poor families. With a social worker mother, the Sutton children had inherited her commitment to service, and knew never to take their good fortune at Christmas for granted. This year, Kinzie, her seven-year-old daughter was thrilled that Santa Claus would make a special visit to a 22-year-old mother named Ashley who worked in a factory raising her 12-month-old son by herself.

    The phone rang on Sunday. A representative from a local organization was calling to say that the aid Ann had requested for Ashley had fallen through. No Santa Claus, no presents, nothing.

    Ann saw the cheer vanish from her children's faces at the news. Without a word, Kinzie ran into her bedroom. She returned, her face set with determination. Opening up her piggy bank, she put all the coins onto the table: $3.30. Everything she had.

    “Mom,” she told Ann, “I know it's not much. But maybe this will buy a present for the baby.”

    At a breakfast meeting the next day, Ann told her coworkers about her daughter's story. To her surprise, staff members began to open their purses and empty their pockets to help Kinzie. By day's end, the story of Kinzie's gift had spread beyond Ann's office. She received a call from an unknown donor. If a seven-year-old could give everything she had, he said, he should at least match her gift 100 to 1. He contributed $300.

    On Christmas Eve, Ann drove through the pouring rain to the small trailer where the Ashleys lived. Then she began to unload the gifts from the car, handing them to Ashley one by one.

    Ashley was very moved. Reflecting on a little girl's generosity, Ashley says she'll one day be able to do something similar for someone else in need. “Kinzie could have used that money for herself, but she gave it away,” Ashley says. “She's the type of kid I'd like my son to grow up to be.”