A、Half a million. B、Seven million. C、Half a billion. D、Seven billion. C选项表明，本题考查数字，听音时应留意与数字相关的信息。短文提到Facebook has half a billio

Each Facebook user has on average 130 friends and shares 70 bits of personal information — including home movies and family photos — every month. With 500 million users detailing their moods and passions online, Facebook is more than a social networking site. It’s a global phenomenon that’s shaping the way people communicate.
    Facebook has half a billion users. That’s huge for a planet of less than 7 billion people.
    What grew as the pet project of Mark Zuckerberg, when he was a student at Harvard, has exploded — gaining eight new users ever second for the past 15 months.
    Facebook has changed the way many people communicate — letting its millions of users share personal thoughts and images with their network of friends.
    Zuckerberg, Facebook’s CEO, said, "People have really gotten connected, not only sharing more information and different kinds but being more open and with more people, and that social norm is just something that’s changed over time. "And people share a lot. Whole lives play out on Facebook. Births, graduations, marriage, even divorce.
    Some experts say that sharing too much information can have downsides — including affecting the way prospective employers may evaluate a job candidate.
    Yet, people share personal information on the site 70 times per month on average.
    Information can easily go viral with the click of a mouse, says Nelson. "Now we have this technology for this one community to talk to another community, and all these different conversations happen at the same time. Almost effortlessly", he said.
    He says the future of social media is mobile. More phones will be able to support Facebook giving even more people access to their online communities from the palm of their hand.
Questions 22 to 25 are based on the passage you have just heard.
22. What is Facebook?
23. How many Facebook users are there all over the world?
24. What is one of the downsides of sharing too much information on Facebook, according to some experts?
25. How often do people share information on Facebook on average?