如图，在直角坐标系中，矩形OABC的顶点O在坐标原点，边OA在x轴上，OC在y轴上，如果矩形OA′B′C′与矩形OABC关于点O位似，且矩形OA′B′C′的面积等于矩形OABC面积的$\frac{1}{4}$，那么点B′的坐标是（       ）

    Young people can have problems with their minds. Some students become worried because they have to study very hard. Others have trouble getting on well with people like their parents and classmates.

    Liu Wei, a Junior 2 student from Hefei, could not understand his teacher and was doing badly in his lessons. He became so worried about it that he started to cut his finger with a knife.

    Another student, 14-year-old Yan Fang from Guangzhou, was afraid of exams. She got very worried when she looked at the exam paper. She couldn't think of anything to write.

    A recent report from Jiefang Daily says about 18% of Shanghai teenagers have mental problems. Their troubles include being worried and very unhappy. And having problems in learning and getting on with people. Many students who have problems won't go for advice or help. Some think they will look stupid (愚蠢) if they go to see a doctor. Others don't want to talk about their secret.

    Liang Yuezhu, an expert on teenagers from Beijing Anding Hospital has the following advice for teenagers:

*Talk to your parents or teachers often

*Take part in group activities and play sports

*Go to see a doctor if you feel unhappy or unwell

①15个苹果，平均放在3个盘子里，每盘放____个。

②15个苹果，每盘放5个，可以放____盘。

查阅资料：①Ca（HCO₃）₂可溶于水

②NaHCO₃ $\underset{\_}{\underset{\_}{△}}$ Na₂CO₃ + H₂O + CO₂↑；Na₂CO₃的热稳定性好，受热不分解。

③不同温度下，Na₂CO₃、NaHCO₃的溶解度如下表：

设计方案：为完成鉴别，同学们分别设计了自己的实验方案