阅读并思考以下的内容:荷兰人菲尔达的炉灶下,几根原木燃着微火。他从火炉旁边的一个纸袋中,抓起一把玉米撒进火焰中,随即,火苗变得旺盛。菲尔达说:“你看,火炉的四周保持清洁,火苗旺盛并且玉米能够完全燃烧。”菲尔达说出了一个事实,即玉米可被当作燃料来使用。菲尔达指出,玉米作为牛的食物,实际上也是一种“燃料”。牛吃 Read and think about the following: A few logs burn with micro-fire under the stove in the Dutch Filda. He grabbed a pile of corn into a flame from a paper bag next to the stove, and immediately the flame became exuberant. Filda said: “You see, the stoves are clean all around, the fire is strong and the corn is completely combustible.” “Filda is telling the truth that corn can be used as fuel. Filda pointed out that corn, as a cow’s food, is actually a ”fuel". Cattle eat