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

材料一：中国是茶树的原产地，也是世界上利用茶树最早的国家。茶树性喜温暖湿润气候，光照是茶树生存的首要条件，不能太强也不能太弱，对紫外线有特殊的嗜好，因而高山出好茶。

    中国茶叶产区划分为西南、江南、华南和江北四大茶区，四大茶区的茶叶产量占全国的比例分别由2009年的30%、39%、36%和5%转变为2014年的38%、33%、23%和6%，茶叶产值分别由2009年的30%、40%、20%和10%转变为2014年的31%、34%、19%和16%。据统计，中国目前茶农已超过800万，另外至少有500万以上从事茶叶销售等第三产业。

材料二：几何重心能够反映地理事物和现象空间分布的变化图，图8a和图8b分别为我国2009～2014年茶叶产量及茶叶产值重心转移路径图。

如图所示，在边长为1的正方形OABC中任取一点P，则点P恰好取自阴影部分的概率为（   ）