C.The gravity of the earth.

　　D.The salt in it.

　　B

　　(2016山东19所名校调研)

　　Wikipedia is a free-access,free content Internet encyclopedia(百科全书),supported and hosted by the non-profit Wikipedia Foundation.Wikipedia is ranked among the ten most popular websites and is considered the Internet’s largest and most popular general reference book.Now,Wikipedia is becoming Wookiepedia as scientists hope the informative website will help us reach out to intelligent life forms.So aliens can learn about the human race.

　　Astronomers would like to beam (播送) the entire contents of Wikipedia into space in the hope of contacting aliens.They want to send messages to hundreds of star systems and planets 20 light years away using radio telescopes.The Search for Extraterrestrial Intelligence Institute,in California,wants to use powerful radio telescopes to try to reach Chewbacca and his mates in a galaxy(银河系)far away.

　　The plans will be discussed by astronomers at the weekend as some scientists fear the reply from ET might not turn out to be friendly.Institute scientist David Black said,“One question is if there are dangerous creatures we might be drawing their attention to ourselves.Another is if we go ahead,what message should be sent?There could be many civilizations out there,but if they are all listening and no one is broadcasting or responding,then nothing will happen.”

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