1012六级听力篇章2原文：
Passage 2

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It’s always fun to write about reserch you can actually try out yourself. Try this. Take a photo and upload it to Facebook, then after a day or so, know what URL link to the picture is and then delete it. Come back a month later and see if the link works. Chances are, it will. Facebook isn’t alone here. Researches at Cambridge University have found out nearly half of the social netwworking sites don’t delete pictures immediately when a user request they be removed. In general, photo-centric websites like Phlica were found to be better at quickly removing deleted photos upon request. Why did deleted photos deck around so long? The problem relates to the way data restored on large websites. While your personal computer only keeps one copy of a file., large-scale services, like Facebook, rely on what are called Content Delivery Networks to manage data and distribution. It’s a complex system where we render data to mutil-intermedia devices usually to speed up access to files when millions of people are trying to access the service at the same time. But because changes aren’t reflected across Content Delivery Networks immediately, ghost copies of files tend to linger for days or weeks. In the case of Facebook, the company says data may hang around until the URL link questioned is reused, which is usually after a short period of time, though obviously that time vary considerably.

Question 30 What does the speaker ask us to try out?
Question 31 What accounts for the failure of some websites to remove photos immediately?
Question 32 When will the unwanted data eventually disappear from Facebook according to the company?