阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。
Xuan paper, known as one of the Four Treasures of Study, first came into 【小题1】 （exist）in Xuan Prefecture in the Tang Dynasty. The traditional skill of making the paper 【小题2】 hand has been passed down through generations. The process takes as many as 108 steps, all of 【小题3】 require a level of delicacy.
Take papermaking master Zhou Donghong for example. He uses a fine screen to filter（过滤）a mixture of water and fibers. He lifts it up, and it's a sheet of paper. It takes him and his partner only 15 seconds 【小题4】 （form）and shape it, but they've devoted 【小题5】 （they）to perfecting the skills for decades.
“There are a lot of tricks of filtering the fibers, and timing is 【小题6】 （difficult）part of all. We have only one chance to filter the right amount of fibers, and only the proper weight guarantees the paper is neither too thin nor too thick, and the margin（差额）for error is 【小题7】 （extreme）small," said Zhou. With just the right degree of thickness, top quality Xuan paper holds ink and water tightly.
The skill of papermaking, 【小题8】 （recognize）as a national treasure, has also proven to be an international one. We felt 【小题9】 great sense of pride as it was listed as a world intangible cultural heritage（非物质文化遗产）by UNESCO in 2009. Since then, in Jingxian County, the making of Xuan paper 【小题10】 （teach）in schools.
