题干

为探究铅中毒对大鼠学习记忆的影响,将大鼠分为四组,其中一组饮水,其余三组饮醋酸铅溶液,60 天后进行检测.检测a:用如图水迷宫(池水黑色,大鼠无法看到平台)进行实验,大鼠从入水点入水,训练其寻找水面下隐蔽平台,重复训练4 天后撤去平台,测定大鼠从入水点到原平台水域的时间;检测b:测定脑组织匀浆铅含量及乙酰胆碱酯酶(AchE)活性.AchE 活性.

检测原理:AchE 可将乙酰胆碱(Ach)水解为胆碱和乙酸,胆碱与显色剂显色,根据颜色深浅计算酶活性.

组别

醋酸铅溶液

浓度/g•L﹣1

脑组织铅含量

/g•gprot﹣1

AchE 活性

/U•mgprot﹣1

到达原平台

水域时间/s

①

0

0.18

1.56

22.7

②

0.05

0.29

1.37

23.1

③

1

0.57

1.08

26.9

④

2

1.05

0.76

36.4

请回答:


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阅读下面短文,掌握大意,然后从1-20各题所给的四个选项(A、B、C和D)中,选出最佳答案。

        My husband, Bob, died in January 2004. His death was unexpected as well. I 1 condolences(哀悼)from people I hadn't heard from in years: letters, cards, flowers, calls, and visits. I took a bad knock with 2. I was so struggling to3the whys and hows of this terrible thing that had happened to my family, knowing in my heart that there really were no 4. It's just all so sad.

        One message5me deeply. I received a letter from my best friend from sixth6 through high school. We had drifted somewhat since 7 in 1959, as she stayed in our home town and I did not. 8 it was the kind of friendship that could quickly resume even if we9touch for five or ten years.

        Her husband, Peter, had died perhaps 20 years ago at a young age, 10her with deep sorrow and heavy 11: finding a job and raising three young children. She and Pete, 12 Bob and I, had shared one of those rare, close, "love-of-your-life-you-can-never-forget" 13.

        In her letter she 14 an anecdote about my mother who had passed away years ago. She wrote, "When Pete died, your dear mother 15me and said, 'Trudy, I don't know what to say...so I'll just say I love you.'"

        She closed her letter to me repeating my mother's words of so long16, "Bonnie, I don't know what to say...so I'll just say I love you."

        I felt I 17 almost hear my mother speaking to me now. What a 18 message of sympathy! How dear of my friend to cherish it all those years and then 19 it on to me.I love you. 20 words. A gift. A legacy(遗赠物).