Readingcanbeasocialactivity．Thinkofthepeoplewhobelongtobookgroups．Theychoosebookstoreadandthenmeettodiscussthem．Now，thewebsiteBookCrossing．comturnsthepageonthetraditionalideaofabookgroup．Membersgoont
Reading can be a social activity．Think of the people who belong to book groups．They choose books to read and then meet to discuss them．Now，the website BookCrossing．com turns the page on thetraditional idea of a book group．
Members go on the site and register the books they own and would like to share．Book Crossing provides an identification number to stick inside the book．Then the person leaves it in a public place，
hoping that the book will have an adventure，traveling far and wide with each new reader who finds it．
Bruce Pederson，the managing director of Book Crossing，says，"The two things that change yourlife are the people you meet and books you read．Book Crossing combines both．"
Members leave books on park benches and buses，in train stations and coffee shops．Whoever findstheir book will go to the site and record where they found it．
People who find a book can also leave a journal entry describing what they thought of it．E-mails are then sent to the Book Crossing to keep them updated about where their books have been found．Bruce Peterson says the idea is for people not to be selfish by keeping a book to gather dust on a shelf athome．
Book Crossing is part of a trend among people who want to get back to the"real"and not the virtual （虚拟）．The site now has more than one million members in more than one hundred thirty-five countries．
29．Why does the author mention book groups in the first paragraph？___
A．To explain what they are．
B．To introduce Book Crossing．
C．To stress the importance of reading．
D．To encourage readers to share their ideas．
30．What does the underlined word"it"in Paragraph 2refer to？___
A．The book．
B．An adventure．
C．A public place．
D．The identification number．
31．What will a BookCrosser do with a book after reading it？___
A．Meet other readers to discuss it．