数学运算 A: 4/9 B: 17/35 C: 101/203 D: 151/301

已知群体中基因型AA、Aa和aa的频率分别为30%，50%和20%，则基因a的频率为： A: 55% B: 45% C: 35% D: 40%

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好氧堆肥堆温较高，一般在 ℃。 A: 25～35 B: 35～45 C: 35～55 D: 55～65

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