Since a secondary source is a source written after an event has occurred, I want to say that the answer is A. Hope this helped!<span />
Humans impact the physical environment in many ways overpopulation, pollution, burning fossil fuels, and deforestation. Changes like these have triggered climate change, soil erosion, poor air quality, and undrinkable water.
Answer: sunlight.
Explanation: When trying to establish the level or extent of correlation or relationship which exists between two variables, the variables are classed as independent and dependent variables. The independent variable is referred to as the variable which causes a change in the value of the other variable (dependent variable). It is also known as the explanatory or predictor variable as it lead to changes in the dependent or predicted variable. In the scenario above, the independent variable is sunlight whose impact leads to changes in the growth level of the plant.
