【单选题】

If there is one thing that could halt the ascent of social networks, it is the thorny question of privacy. This is (1) because it goes right to the (2) of the social-networking business model. In order to attract users, sites need to offer ways for members to restrict the information about themselves that gets shared with a wider (3) .But if a site allows members to keep too much of their information privacy, there will be less (4) that can be turned into profit through advertising and various other means, so the network’s business will (5) .

There is some evidence that people are starting to become more (6) about the way in which they (7) their data, which could have longer-term (8) for the networks’ growth. Research published last year showed that some 60% of adults are restricting (9) to their online profiles.
(10) , the social networks have partly brought this on themselves. In order to offer a better service, many have created (11) sets of privacy controls that allow users to switch between different levels of protection to (12) their online datA、Facebook has excessive controls that can be adjusted to create different levels of (13) .Default settings for younger people on social-networking sites are often more (14) than those for adults to (15) they are protected from unwanted attention.
Social networks (16) applause for developing these fine-grained controls.But their desire for profit can put them on a (17) course with privacy activists, regulators and their users. One bone of contention is social networks’ (18) to draw attention to their privacy statements. The reason for this might be concern about "privacy reassurance": the worry that (19) people to privacy as a potential issue will make them less (20) to share things, even if robust privacy controls are available.
A、deserve B、drawC、demandD、derive