用所给单词的适当形式填空。

    Leonardo da Vinci lived in Italy in the fifteenth and sixteenth centuries. He was a student in Florence, where he studied painting and design. He began a lot of paintings, but he  (not finish) many of them. His picture of the Mona Lisa is  (famous) one in the world.

    Leonardo was interested in many things. He wanted  (know) about everything he saw. He thought the sun doesn't go around the earth. He wrote music. He designed a  (fly) machine 400 years before the first one flew. Many people didn't understand his ideas. It is difficult  (think) that one man can do so much.