题目内容：
"The Internet affords anonymity to its users — a boon to privacy and freedom of speech. But that very anonymity is also behind the explosion of cybercrime that has 1 across the Web.Can privacy be preserved 2 bringing a semblance of safety and security to a world that seems increasingly 3 ?
Last month, Howard Schmidt, the nation’s cyberczar, offered the Obama government a 4 to make the Web a safer place — a “voluntary identify” system that would be the high-tech 5 of a physical key, fingerprint and a photo ID card, all rolled 6 one. The system might use a smart identity card, or a digital credential 7 to a specific computer, and would authenticate users at a range of online services.
The idea is to 8 a federation of private online identify systems. Users could 9 which system to join, and only registered users whose identities have been authenticated could navigate those systems. The approach contrasts with one that would require an Internet driver’s license 10 by the government.
Google and Microsoft are among companies that already have sign-on” systems that make it possible for users to 11 just once but use many different services. 12 , the approach would create a “walled garden” in safe “neighborhoods” and bright “streetlights” to establish a sense of 13 community.
Mr. Schmidt described it as a “voluntary ecosystem” in which individuals and organizations can complete online transactions with 14 ,trusting the identities of the infrastructure that the transaction runs 15 .'"
Still, the administration’s plan has 16 privacy rights activists. Some applaud the approach; others are concerned. It seems clear that such an initiative push toward what would 17 be a license” mentality.
The plan has also been greeted with 18 by some experts, who worry that the “voluntary ecosystem” would still leave much of the Internet 19 .They argue that should be 20 to register and identify themselves, in drivers must be licensed to drive on public roads.
A.swept
B. skipped
C. walked
D. ridden
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