为验证“重力影响生长素的重新分配”。研究人员设计了如下实验：实验材料用具：若干相同的燕麦胚芽鞘尖端、若干相同的去掉尖端的胚芽鞘、一个实验支架（支架的材料托中，放置了6块已编号的相同琼脂块。相邻两个琼脂

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为验证“重力影响生长素的重新分配”。研究人员设计了如下实验：实验材料用具：若干相同的燕麦胚芽鞘尖端、若干相同的去掉尖端的胚芽鞘、一个实验支架（支架的材料托中，放置了6块已编号的相同琼脂块。相邻两个琼脂块之间用不透水的云母片完全割开）。以下实验步骤不恰当的是

A：第一步：将3个胚芽鞘尖端分别放置在实验支架材料托的琼脂块上

B：第二步：将实验支架在单侧光照条件下放置一段时间，光照方向由上至下直射

C：第三步：移走胚芽鞘尖端，然后将材料托的琼脂块取出，分别放在6个切去尖端的胚芽鞘切面的一侧

D：第四步：分别测量和比较不同处理的胚芽鞘弯曲程度

上一题下一题 0.0难度选择题更新时间:2015-07-08 02:39:24

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B

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Subject: Mobile phone problem

Dear Editor,

I am a middle school student. I used to bring a mobile phone with me during school hours. But the teachers think using mobile phone is distraction (分散注意力的事) to students during school hours and also causes so much trouble in class. So now we aren't allowed to bring mobile phones to school.

I find it really inconvenient (不方便的)。 My parents feel unhappy because they can't get in touch with me(不能与我有联系) . But I can't make our school change this rule. What do you think I should do to solve this problem?

Liu Fengyi

Liu fengyi's occupation (职业)	____
Purpose (目的) for writing the e-mail	____
The school rule	Students aren't allowed to ____
Thing that Liu Fengyi used to do	She used to ____
Reason(原因) why Liu Fengyi's parents are unhappy	They can't ____

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