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简述基因表达调控的生物学意义？

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It's getting colder by the minute.If we don't do something soon, We'll all 1 to death.Prince Hans... - Princess Anna is...Dead. What...?What happened to her?She was killed by Queen Elsa.Her own sister.At least we got to say our marriage 2...before she died in my arms.There can be no doubt now,Queen Elsa is a monster and we are all in 3danger.Prince Hans, Arendelle looks to you.With a heavy heart,I charge Queen Elsa of Arendelle with 4and sentence her to death.Hurry Up!She's dangerous. Move quickly and be careful.The Door not open!What is it, 5? Hey, watch it.What's wrong with you?I don't understand you when you talk like that.Ah! Stop it! Put me down!No, Sven! We're not going back!She's with her true love.What the...Anna!Come on,come on ,boy.

阅读《假如给我三天光明》，将自己对生命意义的认识、对生命的感悟写出来，不少于500字。

在单缝夫琅禾费衍射实验中波长为λ的单色光垂直入射到单缝上．对应于衍射角为30°的方向上，若单缝处波面可分成 3个半波带，则缝宽度a等于 [].

A. 1.5λ
B. 2λ
C. 3λ
D. 6λ

波长λ=500nm的单色光垂直照射到宽度a=0.25 mm的单缝上,单缝后面放置一凸透镜,在凸透镜的焦平面上放置一屏幕,用以观测衍射条纹.今测得屏幕上中央明条纹一侧第三个暗条纹和另一侧第三个暗条纹之间的距离为d=12 mm,则凸透镜的焦距f为 [ ]

A. 2 m;
B. 1 m;
C. 0.5 m;
D. 0.2 m;
E. 0.1 m.