Scientific Method Question

In a controlled experiment, the researcher typically manipulates one variable, called the independent variable, to determine how this variable affects the final outcome, called the dependent variable. In the following hypothetical example, a researcher applies varying amounts of fertilizer (0, 2, 4, 8, 10 units) to potted tomato plants. All other variables that may affect the outcome (watering, temperature, sunlight, plant size, etc.) are kept the same from pot to pot. At the end of the growing season, the tomatoes grown on each plant are weighed to determine which fertilizer level produces the largest tomato yield. Which variable was the independent variable and which was the dependent variable?

1. Independent = Fertilizer amount, Dependent = Temperature
2. Independent = Temperature, Dependent = Yield
3. Independent = Fertilizer amount, Dependent = Yield
4. Independent = Yield, Dependent = Fertilizer amount