题目内容：
共用题干Global Warming
Few people now question the reality of global warming and its effects on the world's climate.Many scientists______(1)the blame for recent natural disasters on the increase______(2) the world's temperatures and are convinced that,more than______(3)before,the Earth is at______(4)from the forces of the wind,rain and sun.______(5)to them,global warming is making extreme weather events,______(6)as hurricanes and droughts,even more______(7)and causing sea levels all around the world to______(8).
Environmental groups are putting______(9) on governments to take action to reduce the ______(10) of carbon dioxide which is given______(11) by factories and power plants,thus attacking the problem at its source.They are in______(12) of more money being spent on research into so-lar,wind and wave energy devices,which could then replace existing power______(13).
Some scientists,______(14) believe that even if we stopped releasing carbon dioxide and other gases into the atmosphere tomorrow,we would have to wait______(15) hundred years to notice the results.Global warming,it seems,is here to stay.
3._________
A:yet
B:never
C:once
D:ever
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