根据下面材料，在空白处填入1个适当的单词或括号内所给单词的正确形式。

The oil-paper umbrella has a history of over 1,000 years in China. There are different （1） （story）about the invention of the umbrella in China. The most popular one has something to do with Lu Ban. It’s said that once he and his wife visited the West Lake. It started raining suddenly. His wife said, “Let’s have （2） competition. Before sunrise tomorrow, the one who comes up （3） a good way to visit the West Lake even on rainy days will be the winner.” Lu Ban （4） （think）it was easy. He collected some tools and materials. Then he spent the whole night （5） （build）pavilions（亭子）around the lake. He was quite proud of his work.

The next morning, （6） Lu Ban talked about his achievements and felt proud, his wife held something unusual in her hand. It could be opened into a round shape. Lu Ban was （7） （surprise）. He found that the object, made of silk and bamboo, could be opened and closed （8） （easy）. It was light, beautiful and easy to carry. Lu Ban said, “You win. Your invention can protect us from rain better.” So the umbrella （9） （invent）.

Later, people began to use paper, which was （10） （cheap）than silk. To make the umbrella water-proof, people brushed a kind of oil on the surface. So the oil-paper umbrella appeared.