[originaltext] Have you ever heard of the Vikings? They were sea travellers

Have you ever heard of the Vikings? They were sea travellers from Norway. More than a thousand years ago, they made three important geographical discoveries.
    (19) The Vikings’ first major discovery occurred in the ninth century. A man called Naddod was on his way from Norway to the Faroe Islands, north of England, when his ship was caught in a storm. The storm blew the ship west for several days. When the weather cleared, Naddod found himself on the coast of a new land. Later, Viking travellers named it Iceland.
    In 982, a Viking called Eric the Red sailed west in search of new land. (20) Five hundred miles west of Iceland, he and his men reached an icy rocky mass of land. They sailed around it until they reached the western side. Here, they found some green areas, so they named the island Greenland.
    Then, in 1001, the Vikings made their most important discovery. The son of Eric the Red, named Leif Ericson, had heard rumors about land west of Greenland. He sailed west and soon found it. He and his men landed in three places. They called the first one Helluland, which means land of flat stones. The Vikings then sailed south and made their second landing. They named this place Markland. The third landing was at a place they called Vinland. Leif Ericson and his men were the first Europeans to walk on the shores of North America, almost 500 years earlier than Columbus.
Questions 19 to 21 are based on the passage you have just heard.
19. What do we learn about the Vikings?
20. What does the passage say about Greenland?
21. What does the speaker mainly talk about?