题目内容：

阅读下面短文，在空白处填人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 1. (exist) in Xuan Prefecture in the Tang dynasty. The traditional skill of making the paper 2. hand has been passed down through generations. The process takes as many as 100 steps, all of 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 4. (form) and shape it, but they’ve devoted 5. (them) to perfecting the skills for decades.

“There are a lot of tricks of filtering the fibers, and timing is the 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 for error is 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, 8. (recognize) as a national treasure, has also proven to be an international one. We felt 9. great sense of pride as it was listed as a world intangible culture heritage(非物质文化遗产) by UNESCO in 2009. Since then, in Jingxian County, Xuan papermaking  10.(teach) in schools.