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。

In ancient times, Chinese ancestors liked to steam or boil food. It was difficult for them to use spoons to get vegetables in the soup. So they 【小题1】(clever) invented chopsticks to pick up food. Development of chopstick has experienced a long history. Chopsticks only became two sticks of the same 【小题2】(long) in the Shang Dynasty (16th-11th century BC).

As chopsticks feature the coming of civilization to food culture, the invention also 【小题3】 (have) many scientific theories：The lever (杠杆) principle of mechanics is applied into practice. The point【小题4】 two sticks crossed is the pivot (支点) of the lever. An interesting experiment shows that many joints and muscles are being exercised 【小题5】 you use it. They certainly make you cleverer, 【小题6】(do) they?

Chopsticks are small but they 【小题7】(admire) by many people in the world. Nowadays, chopsticks serve many new functions besides tableware. For example, you can buy a pair as a gift to your friends and relatives. In Chinese, it reads kuaizi, 【小题8】(mean) to have sons soon, so a newly-married couple will be very happy to accept it as their wedding gift. Skillful artists paint beautiful scenery on chopsticks 【小题9】(make) them like fine artworks. Many people love to collect them too. Many foreigners are interested in 【小题10】puzzled about how to use it. They need to practice a lot.