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下面短文中的划线部分是错误的，请改正，但不得改变原文意思。
Children and adults enjoy play with kites.             1．
There are a lot of kite festivals and competitions in China,
Japan and many others countries. But kites are not just playthings.       2．
They can be useful on many other ways. Kite flying has       3．
been popular in China since more than             4．
two thousands years. Scientists have been             5．
interesting in kites for a long time. They have used them       6．
for studying weather and for testing new kinds of flying machines.
Recently, scientists have develop many new kinds of kites.       7．
Some of them can pull boats, or lift a man easy. Some can       8．
fly like a plane. Some kites are really beautiful work of art,       9．
and people love it. Kite flying is not only an art but also a science.       10．