问题
单项选择题
下述关于航空噪声危害大的理由叙述中，错误的是（）。
A.飞机起飞或降落时的噪声级最大
B.超声速飞机低空飞过时产生轰声
C.喷气机的噪声是以金属性的低频成分为主
D.喷气机的声功率为10kW以上，声功率级高达160dB以上
答案
参考答案：C
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下述关于航空噪声危害大的理由叙述中，错误的是（）。
A.飞机起飞或降落时的噪声级最大
B.超声速飞机低空飞过时产生轰声
C.喷气机的噪声是以金属性的低频成分为主
D.喷气机的声功率为10kW以上，声功率级高达160dB以上
参考答案：C
It’s very important that we all recycle (再利用). In nature, everything ___26___ again. For example, when an animal dies, it becomes ___27____ animal’s food. Nothing is wasted. But humans have created things like plastic bags ___28___ can’t be broken down by nature. Our rubbish kills animals and __29___ water and soil. ___30___ we continue making too much rubbish, the problem will only get worse. If nature can’t reuse the rubbish, we must recycle __31__. We should clean up the rubbish we’ve made because nature can’t. Recycling is also the right thing to do for another reason. The earth is rich in natural materials like water and trees, __32 __ these materials are not endless. We use up our natural materials much _ _33 __ than the earth is able to reproduce them. For example, each year we cut __34 __ more that 6,000 square miles of forest. But it takes an average of 25 years for a new tree __35__. Recycling can help us save the earth, so let’s take action right now.
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