题目

阅读下列短文, 从每题所给的A、B、C、D四个选项中选出最佳选项。Give yourself a test. Which way is the wind blowing? How many kinds of wildflowers can be seen from your front door? If your awareness is as sharp as it could be, you'll have no trouble answering these questions.Most of us observed much more as children than we do as adults. A child's day is filled with fascination, newness and wonder. Curiosity gave us all a natural awareness. But distinctions that were sharp to us as children become unclear;we are numb(麻木的) to new stimulation(刺激), new ideas. Rele下列气体与空气混合后遇明火，可能发生爆炸的是（ ）A．氧气B．氮气C．氢气D．二氧化碳