根据短文内容，选择正确答案。
Leonardo da Vinci was born on April 15, 1452 in Italy. He is best known as an artist today. One of his famous paintings is called Mona Lisa. However, Leonardo had many other natural abilities. He was also a great inventor. Many of his inventions have become important in modern daily life.
Although Leonardo hated war, he invented many different machines used for war. His most special invention was the machine gun, which was produced and used in war many years later.
By watching the way birds fly, Leonardo tried to find out the secret of flying. Among his sketch (素描) we can see several objects. We consider them as modern flying machines.
Leonardo spent many hours thinking about how to make good use of time. He developed ideas for labor-saving machines like cutting machines.
Leonardo was a strange man. He didn't eat any meat, which was very unusual in those times. He never published(发表) his ideas and scientific discoveries. He usually used mirror writing, which looks like writing in a mirror, starting from the right side of the page and moving to the left.
We have very little of his work today. Leonardo finished only a few of his paintings. He left many unfinished because he thought they were not perfect. No one in his life time knew how great Leonardo was. We now believe, however, that he was one of the cleverest men the world has ever known.