间壁稳态传热时, 各层的温度降与各相应层的热阻成____。
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金属和非金属的导热系数都随温度升高而减小。
A. 对
B. 错
定态的圆筒壁传热，热通量为常数。
A. 对
B. 错
What can help to change the situation of agriculture market to work for the poor?
A. Digital technology
Banks
C. Extension workers
D. Local cooperative
Which of the following statements about Africa is not true?
A. Hundreds of millions of African people live on farming.
B. Half of the labor in Africa produces food.
C. Africa imports $40 billion worth of food this year.
D. African smallholders failed to grow as much food as they could.
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