A、It is a platform for sharing ideas on teaching at the University of Illinois. B、It was mainly used by scientists and technical

In early 1994, when Mark Andreessen was just 23 years old, he arrived in Silicon Valley with an idea that would change the world. As a student at the University of Illinois, he and his friends had developed a program called Mosaic, which allowed people to share information on the world wide web. Before Mosaic, the web had been used mainly by scientists and other technical people, who were happy just to send and receive text. But with Mosaic, Andreessen and his friends had developed a program which could send images over the web as well. Mosaic was an overnight success. It was put on the university’s network at the beginning of 1993. And by the end of the year, it had over a million users. Soon after, Andreessen went to seek his fortune in Silicon Valley. Once he got there, he started to have meetings with a man called Jim Clark, who was one of the Valley’s most famous entrepreneurs. In 1994, nobody was making any real money from the Internet which was still very slow and hard to use. But Andreessen had seen an opportunity that would make him and Clark rich within two years. He suggested they should create a new computer program that would do the same job as Mosaic but would be much easier to use. Clark listened carefully to Andreessen, whose ideas and enthusiasm impressed him greatly. Eventually, Clark agreed to invest three million dollars of his own money in the project, and to raise an extra fifteen million from venture capitalists who were always keen to listen to Clark’s new ideas.
19. What do we learn about Mosaic?
20. What did Andreessen do upon arriving in Silicon Valley?
21. Why were venture capitalists willing to join in Clark’s investment?