题干

某校生物兴趣小组为了“探究烟草浸出液对水蚤心率的影响”,进行实验研究如下:取同种品牌、同一批次的香烟四支,取每支香烟烟丝的1/2分别放在20mL、30mL、40mL、50mL,蒸馏水浸泡1天,用其浸出液处理水蚤,观察水蚤的心率变化。

组别

清水

50 mL

40 mL

30 mL

20mL

10s内心跳次数

35

36

37

39

41

下列有关实验的叙述中错误的是(    )

A:每组实验均只需准备一只水蚤

B:清水组是本实验组的对照组

C:烟草浸出液对水蚤心率有促进作用

D:一定浓度范围内,水蚤心率随烟草浸出液浓度升高而加快

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答案(点此获取答案解析)

A

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    His name was Fleming, and he was a poor Scottish farmer. One day late in the afternoon, while working to support his family, he heard a cry for help coming from a nearby pond(池塘). He dropped his tools and ran to the pond. There, up to his neck in the water, was a terrified boy, crying and struggling to free himself. Obviously the boy did not know how to swim. Fleming jumped into the pond and quickly swam toward the boy. He saved the boy who could have been a terrible death.

    The next day, a very cool carriage pulled up to the Scotsman's house. A well-dressed noble man stepped out and introduced himself as the father of the boy Fleming saved the day before.

   “I want to repay you,” said the nobleman. “You saved my son's life.”

   “No, I can't accept any payment for what I did,” the Scottish farmer replied, waving off the offer.

    At that moment, the farmer's own son came to the door of the farm house, confused by who was visiting them.

  “Is that your son?” the nobleman asked.

  “Yes,” the farmer replied proudly.

  “I'll make you a deal. Let me take him with me. I promise you that I will give him a good education. If the boy is anything like his father, he'll grow up to be a man you can be proud of.”

    And he did. In time, Fleming's son graduated from St. Mary's Hospital Medical School in London and went on to become a famous doctor.

    Years later, the nobleman's son became seriously ill. Who saved him? The farmer's son did.

    It's important to help people no matter how successful you are in life. You never know when you are going to be the one who needs the help.