In China， writing brushes， ink sticks， paper and ink stones are called the Four Treasures of Study．Among the high﹣quality （质量） treasures， the writing brush produced in Huzhou， the ink stick produced in Huizhou， the xuan paper made in Xuancheng and the ink stone made in Duanxi are the best﹣known．

    The writing brushes can be used to draw the pictures on painted potteries （陶器）．They are mainly made of the hair of animals．Those made of wool are called yanghao and those made of the weasel's （鼬）tail hair are called langhao． Their artistic effects （效果） in writing and painting cannot be copied by any other pens．

    The ink stick is the pigment （颜料） used in writing and painting．The ink stick produced in Huizhou is of high quality． A story goes like this： Two famous skilled men Xi Chao and his son produced a kind of high﹣quality ink stick． As a result， the Emperor Li Yu in the Southern Tang Dynasty agreed to give them the family name"Li"， From then on， the fame of the Li Ink Stick was widespread． In the Song Dynasty， its producing area was changed into Huizhou， and it was then called the Hui Ink Stick．

    Paper is among the four great inventions in ancient China． The famous xuan paper appeared in the Sui and Tang dynasties． In Xuanzhou， Anhui Province where the xuan paper is produced，it's said that Cai Lun's pupil Kong Dan took the job of producing paper but failed to make perfect white paper． Later he happened to see the ebony （檀木） in the rivers． It was wet with the water and turned white． Then he used the bark （树皮） to produce the world﹣famous xuan paper．

    The ink stone was already very popular in the Han Dynasty． The Ming and Qing dynasties saw the appearance of the Four Famous Ink Stones一Duan Ink Stone， She Ink Stone， Tao Ink Stone and Chengni Ink Stone． They can not only be used in writing and painting but also for admiration．

（1）What are the writing brushes mainly made of？　　

（2）Why did Xi Chao and his son get the family name from the Emperor Li Yu？　　

（3）What does it in paragraph 3 refer to （指的是）？　　

（4）How did Kong Dan find the way to make the famous xuan paper by accident？　　

（5）When did the Four Famous Ink Stones appear？　　

（6）What's the title （标题） for the passage？ （ 不超过10个词）