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 scientists1the blame for recent natural disasters on the increase2the world's temperatures and are convinced that,more than3before,the Earth is at4from the forces of the wind,rain and sun.5to them,global warming is making extreme weather events,6as hurricanes and droughts,even more7and causing sea levels all around the world to8.
Environmental groups are putting9on 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 in12of more money being spent on research into so-lar,wind and wave energy devices,which could then replace existing power13.
Some scientists,14believe that even if we stopped releasing carbon dioxide and other gases into the atmosphere tomorrow,we would have to wait15hundred years to notice the results. Global warming,it seems,is here to stay.
3._________
A: yet
B: never
C: once
D: ever
参考答案：
答案解析：