A、Because they thought he was still in China. B、Because they thought he was put into prison. C、Because they thought he was worki

Marco Polo was 17 years old when he set out on the most famous journey in history. In 1271 he left Italy with his father and his uncle, and he spent more than three years crossing the Middle East and Asia. He wanted to see Mongolian ruler, Kublal Khan.
    Marco arrived in China in 1275. The Khan liked him at once, and Marco became an important government official. He traveled all over the country and brought back information for the Khan.
    It was 24 years before Marco returned to his home in Venice. When he finally arrived there, his family and friends were surprised to see him again, because everybody thought that he had died many years before.
    At first, people did not pay much attention to the stories Marco told. Then, when Venice went to war with Genoa, Marco joined the Navy. He was caught by the enemy, and put into jail. While he was there, he told his stories to his fellow prisoners to pass the time. One of the prisoners was a writer called Rustichello, and he wrote down Marco’s adventures in a book. This book is called "The Travel of Marco Polo", and it is still famous today.
    Marco did not make any more journeys after his book was published, but he dreamed that one day he would returned to China. Almost seven centuries later, his dream came true. In the 1980s, the historical film "Marco Polo", made by a Sino-Italian team, brought Marco to meet Chinese audience.