Questions下列各are based on the following passage．Rumors have swirled for years about the mystical phone, which FacebooK introduced at its headquarters today．For the financial sake of Facebook, its imperative that the new phone-- manufactured by HTC, carried by AT&T and sporting an Android operating system--sells well．Its the linchpin(关键) in the social-networking companys pursuit of mobile ads, The $ 99 phone goes on sale April l2．The phone/service features Home (facebook, corn/home), downloadable software that brings the Facebook experience to several Android devices: HTC One X, HTC One X +, Samsnng Galaxy SIII and Samsumg Galaxy Note II．At first blush, the new phone could find a receptive audience among the nnder-25 crowd, which is comfortable with having their mobile devices within reach at all times．Facebook chafes at suggestions that s and twentysomethings are leaving the social network, so a phone immersed in news updates and other Facebook features might go over well．Facebook, the No．2 mobile-ad publisher in the U．S．behind Google, last year accounted for 9．5% of the $ 4．1 billion mobile ad market．Its expected to take I3% of the $ 7．3 billion market this year,estimates researcher eMarketer．A phone could 'hard wire' the Facebook experience on a mobile device, increasing consumers time on the service, ysts say．But the experience has to be more than a branded device, they say．Branded phones from Barclays and Mary Kay did not fare well．'It cant be just about the hardware,' says Phillip Redman, mobile yst at Gartner．'It can do two things for success: Change the business model and give it away to its best users; or design it for low-cost or no-cost calls among Facebook friends．' Facebooks entry is one in a glut(供过于求) of recent smartphone contestants．New models from Samsung (Galaxy $4), HTC (One) and BlackBerry (the Q10 keyboarD． highlight a bumper spring crop.Apples rumored iPhone 5S or iPhone 6 lurks in the shadows, 'The handset market is very competitive,' says Clark Fredricksen, vice president at eMarketer．'Samsung, Apple and Android all are gaining market share, and boast computing platforms to feed into (the) mobile market．It remains to be seen if Facebook will gain popularity．' Facebook boasts 1 billion members, 30% of which are mobile-only users, according to market researcher ComScore．It was also the No．1 mobile app in the U．S．in February in terms of engagement, accounting for 24% of all time spent on mobile apps--27%, ff you include Instagram．Why is the new phone so crucial to Facebook?