元青花之谜
①元代青花瓷从诞生之日起，就给后世留下了众多的谜团。
②第一个谜就是它的纹饰为什么是蓝色的。蒙古人尚白尚蓝，是受波斯文化的影响。13世纪初，成吉思汗异军突起，他和他的继承者多次征服西亚、中亚，打通了中西文化交流的通道。大批阿拉伯人、波斯人和突厥人涌入中国，其中包括工匠、天文学家、医学家等，他们带来了西域的文化。蓝色是西域波斯文化的主色调，今天去中东我们依然可以看见到处都是以蓝色为主色调的建筑。
③第二个谜就是它的发展没有初创期，没有萌芽期，它是突然成熟的。你看见它的时候，它就不是襁褓中的婴儿，而是亭亭玉立的大姑娘了。这有多种解释：有的说元青花不是元代早期出现的，而是元代中晚期出现的，那个时候，波斯人带来了现成的原材料和成熟的工艺，元青花直接受波斯文化的影响。另外一种说法是元代以后有大量北方工匠南迁，他们的绘画能力都比较强，他们来到南方的景德镇驻扎下来，在景德镇漂亮的瓷胎上重新开始作画，就跟一个画家到另外一个地方画画似的，只不过是换了纸，换了颜料而已，技艺上没有什么区别。元青花的这种突然成熟，从学术角度讲，至今还有很多问题尚待研究。
④第三个谜是元青花纹饰为什么题材众多。元青花跟其他瓷器的题材表现不一样，它的题材尤其多。其实元青花早期的题材大都是花卉、鸟兽、龙凤，后期才出现了人物题材。后期画人物的第一个原因是元青花受元曲和小说的影响，注意展现情节。第二个原因是在元朝后期，朱元璋没有拿下江山之前，曾长时间驻扎在景德镇。他对景德镇的瓷器生产应该有过影响，由于他对战争故事的关注，以人物为纹饰题材的作品开始逐渐增多。
⑤第四个谜是元青花造型硕大，大件瓷器特别多，如大盘、大罐、大瓶。元青花大器特别多有一个原因，就是跟蒙古人的性格有关。蒙古人性格粗犷，不拘小节。比如江西高安出土的元青花当中有一个“把杯”，所谓“把杯”，就是高足杯，下面的足可以用手攥着。为什么做成这样的呢？因为元人是马上民族，他骑在马上，一只手腾出来就可以攥住这个杯子。“欲饮琵琶马上催”就是这个感觉。高安出土的这个“把杯”，上面写着两句诗，非常有意思：“人生百年常在醉，算来三万六千场。”
⑤元青花自其诞生之日起，就迅速繁荣起来。后来的明清两代，瓷器都以青花为主。元青花是汉族文化、西域波斯文化、蒙古文化的结晶。

     Mabel was a naughty boy and he was not good at his study. “Could do better” were usually the 1 at the bottom of his report card. His parents 2 Mabel's marks a lot. How they wished Mabel made a little progress. But whenever they got his report card, they were quite disappointed, 3 their heads.

     At the end of the term, the report card would be sent home. Mabel wished to find a safe place away from the 4 faces of his parents. One morning, when Mabel was still in bed, his mother rushed into his room, holding the report card in hand. “Well done, son. You are number one in the class. You are our 5.” She gave Mabel a big kiss. Mabel could not believe it, 6 he looked at the report card carefully.

     Very soon, Mabel found out it was Manuel's report card, not his. The teacher had made a 7. His mother had left, busying calling all the family about the 8 news. Mabel wondered what the right thing to do was. He thought for a while, whether to please his parents 9 to be an honest boy. Finally, he decided to tell his parents the 10.

如图，AB是⊙O的直径，AC是弦，∠BAC的平分线AD交⊙O于点D，DE⊥AC，交AC的延长线于点E，OE交AD于点F．

（1）求证：DE是⊙O的切线．

（2）若$\frac{AC}{AB}$=$\frac{2}{5}$，求$\frac{AF}{DF}$的值．

“黄梅时节家家雨，青草池塘处处蛙”形象的描绘了我国哪个地区的景象（    ）