Which animals will produce less methane?
A. Cattle and sheep.
B. Pigs and chickens
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Why does the speaker suggest that oil, natural gas and coal be used less?
A. Those sources of energy are limited.
B. Those sources of energy produce more CO2 emissions.
Where does green electricity come from?
A. Renewable energy.
B. Advanced technology.
对下面的每一种滤波器指标，选择满足FIRDF设计要求的窗函数类型和长度。(1) 阻带衰减20 dB，过渡带宽度1 kHz，采样频率12 kHz；
A. 三角窗，N = 37
B. 矩形窗，N = 11
C. 哈明窗，N = 11
D. 布莱克曼窗，N =22
对下面的每一种滤波器指标，选择满足FIRDF设计要求的窗函数类型和长度。(2) 阻带衰减50 dB，过渡带宽度2 kHz，采样频率5 kHz；
A. 三角窗，N = 35
B. 矩形窗，N = 9
C. 哈明窗，N = 9
D. 布莱克曼窗，N =14
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