Fill in the Blanks cloze-test advancedOnline version Cloze Test C1 by Nicolas De Panicis 1 that Troughout of thouhg have far wheter that neither large history we have wondered about the possibility of life beyobend the Earth . Is is only in recent years , however , that advances in technology revealed the existence of extrasolar planets ( or 'exolanets' ) , is to say , planets which orbit not our own sun , but other stars in the universe . so , astronomers have identified a few thousand exoplanets , but believe that billions more exist . Although many astronomers believe that a number of planets in the universe are capable supporting some kind of iving organism , or not life has developed on any of them is not yet known . An essential requirement for life is liquid watr . If a planet is to have liquid water on its surface , its temperature must be too hot nor too cold . However , such a planet , other the Earth , has yet to be discovered . It may be found in the near future , . Move on to your next mission if you really wnat to know more .
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