题目内容：
Questions are based on the t'ollowing passage．As high school students flock to social networking sites, campus police are scanningtheir Facebook and MySpace pages for tips to help break up fights, monitor gangs andprevent crime．
Some students object to police looking over their shoulders． But officers responsiblefor school safety say routine checks of the online forums often add to the knowledge theyobtain from hallways or schoolyards．
In recent years, school administrators have blamed some campus fights on Internetconflicts and urged parents to keep watch on their children's computer activity． But studentswho use the Web to let their 500 closest friends know what they are doing at all times aresometimes surprised that police are watching, too．
Police don't have special privileges on Facebook or MySpace． Students who want to gounobserved can change privacy settings so that their profiles are displayed only to a list ofapproved people． But the default (默认) settings leave those profiles open to many Internetusers (in the case of Facebook) or all of them (in the case of MySpace)．
Employers and college admissions counselors have examined online profiles of studentapplicants for some time． Police across the country have been doing the same for the pasttwo or three years, said Kevin Quinn, a spokesman for the Minnesota-based National
Association of School Resource Officers．
"If you're already familiar with the technology, it doesn't take you but a couple ofminutes to hook into the student population and keep an eye on things," Quinn said．
An expedition into a thicket (丛林) of MySpace profiles found high school studentsdiscussing drugs, sex and fights． It was all publicly available (although in language thatcaused a reporter to blush)．
Late last month, Fairfax County police announced the arrests of seven Chantilly areateenagers for trying to recruit Franklin Middle School students to a gang． That investigationwas aided when a student showed the school resource officer gang symbols littering one ofthe suspect's Myspace profiles．
Fairfax police say they pride themselves on addressing issues in schools before theydevelop into major problems． Keeping an eye on Facebook and MySpace has become anextra tool in that effort, they said．
Police officers scan social networking sites like Facebook or MySpace because ___________． A．they have some special privileges to do so
B．they may detect gang-fighting through the Net
C．it is easier to solve students' conflicts online
D．it is their duty to protect students' privacy
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