Which of these explains an independent variable? Help

Which table best shows the impacts resulting from human activity? impact of human activities human activity impact forest area cleared to construct an airport increase in oxygen level vegetation cleared to construct an oil mine increase in pollution impact of human activities human activity impact forest area cleared to construct an airport increase in sound pollution vegetation cleared to construct a power plant contamination of water impact of human activities human activity impact beehives cleared from urban areas increase in vegetation dams constructed on a river increase in fish population impact of human activities human activity impact beehives cleared from urban areas increase in bird population dams constructed on a river better quality of water

How does upwelling affect coastal fisheries? upwelling damages nutrient supplies at coastal fisheries as the warm, nutrient-rich surface water is replaced by nutrient-poor, cold water. upwelling damages nutrient supplies at coastal fisheries as the cold, nutrient-rich surface water is replaced by nutrient-poor, warm water. upwelling improves the nutrient supply at coastal fisheries as the warm, nutrient-rich surface water replaces the nutrient-poor, cold water. upwelling improves the nutrient supply at coastal fisheries as cold, nutrient-rich water replaces the warm, nutrient-poor surface water.

Which statement describes how favorable traits in a population relate to natural selection? they are the only traits that ever exist in the population. they build in the population over time. they are rarely passed on to offspring. they are found only in a few individuals within the population.