A、For the research for the US military. B、For the research for a handful of universities. C、For the research for some government

(19)The Internet began in the 1960s as a small network of academic and government computers primarily involved in research for the US military. Originally limited to researchers at a handful of universities and government facilities, the Internet has quickly become a worldwide network providing users with information on a range of subjects and allowing them to purchase goods directly from companies via computer.(20)By 1999, 84 million US citizens had access to the Internet at home or work. More and more Americans are paying bills, shopping, ordering airline tickets, and purchasing stocks via the computer over the Internet. Internet banking is also becoming increasingly popular. At present, 14 percent of Internet households conduct their banking by means of the Internet, and the figure is expected to double during the next two or three years.
    Increasing commercial use of the Internet has increased security concerns. With a credit or debit card, an Internet user can order almost anything from an Internet site and have it delivered to their home or office. Companies doing business over the Internet need sophisticated security measures to protect credit cards, bank accounts, and social security numbers from illegal access as they pass across the Internet. Any organization that connects its networks to the global Internet must carefully control the access point to ensure that outsiders cannot break into the organization’s internal networks or gain illegal access to the organization’s computer systems and data.
Questions 19 to 21 are based on the passage you have just heard.
19. What was the original purpose of the Internet?
20. How many US citizens had access to the Internet by 1999?
21. What is this passage mainly about?