4. Most people have flown a kite or have seen one ride and dip(下降) in strong spring wind. Not so many people know that kites were first made in China thousands of years ago. The ancient (古代的) Chinese were making and flying kites even before they were writing. A long time ago, the Chinese made kites to use in wars. They would fly these war kites in the dark. The kites were fixed (固定) so that they made strange sounds. Men who were at war with them would hear these sounds and run away. They thought those strange sounds were made by gods(神) in the sky. The ancient Chinese also flew kites to bring good luck and to make their crops（农作物） grow rich and tall. Sometimes they tied long strings (细绳) and hooks (钩) to their kites. Then they would fly the kites over water, letting the hooks hang down to catch fish. The Chinese use sticks（树枝）, strings（线） and paper for their kites. Some of these kites look like animals or trees. Others look like birds or houses. The Chinese usually use ____ for their kites.