Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 11 to 15.

Few people now question the reality of global warming and its effects on the world's climate. Many scientists (11) ________ the blame for recent natural disasters on the increase in the world's temperatures and are convinced that, more than ever before, the Earth is at risk from the forces of the wind, rain and sun. According to them, global warming is making extreme weather events, such as hurricanes and droughts, even more (12) ________ and causing sea levels all around the world to rise. Environmental groups are putting pressure on governments to take action to reduce the amount of carbon dioxide which is given (13) _________ by factories and power plants, thus attacking the problem at its source. They are in favour of more money being spent on research into solar, wind and wave energy devices, (14) _________ could then replace existing power stations. Some scientists, (15) ________ believe that even if we stopped releasing carbon dioxide and other gases into the atmosphere tomorrow, we would have to wait several hundred years to notice the results. Global warming, it seems, is to stay.