稻田中除了水稻外，还有杂草、田螺等生物。稻田中经控制后的有害_爱下问搜题

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问题填空题

稻田中除了水稻外，还有杂草、田螺等生物。

稻田中经控制后的有害生物密度与所需的防治成本有关，并影响作物的价值。

图中曲线（）（填“Ⅰ”或“Ⅱ”）表示将有害生物控制在不同密度时的防治成本。若将有害生物密度分别控制在图中A、B、C三点，则控制在（）点时收益最大。

答案

参考答案：Ⅰ；16

解析：

当经控制后有害生物的密度较低时，作物的价值也较大，防治成本也大。当有害生物的密度较大时，作物的价值下降更快更明显，若在有害生物密度很低时使之更低，也将更加不易，使防治成本迅速增大。所以Ⅰ表示将有害生物控制在不同密度时的防治成本，Ⅱ表示将有害生物控制在不同密度时的价值。

选择题

向盛有10mL氢氧化钠溶液的烧杯中逐滴滴加稀盐酸，下列图像能体现溶液的pH变化情况的是（）

完形填空

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