【正确答案】 B

【答案解析】[听力原文]
As you listen to this, flip your eyes over to the window. The sky is clear, the wind light, and the sun brilliant. Or maybe not—mother nature is full of surprises these days. The calendar says it"s spring, but there could just as easily be a winter snowstorm, a summer heat, or an autumn cold snap. Almost in an instant, it seems, the weather shifts from one season to another. And wherever it swings, it seems increasingly likely to be extreme.
Consider what mother nature slung our way last year in May, typically the second worst month for tornadoes. In less than 24 hours, more than 70 hellholes of wind rampaged through Oklahoma and Kansas, killing 49 and causing more than $ 1 billion in damages. In June, it was heat, as the Northeast began roasting through weeks of the worst drought since the 1960s;256 people died. This yea in January, blizzards pounded the US from Kansas to the Atlantic Ocean. In April, 25 inches of snow fell on parts of New England.
Why has our weather gone wild? It"s the question everyone"s asking, but a very tough one to answer. Although many scientists still aren"t convinced that it has gone wild, some have begun saying—cautiously, hesitantly—that extreme weather events are occurring with more frequency than at any time in this century, events consistent with the profile of a warming world. "The mean temperatures are going up. The key question is: What will it do locally? I think we are going to start feeling its effects in the changes on extremes." some scientists say.