The function below models the correlation between the number of hours a plant is kept in sunlight (x) and the height (y), in mm, to which it grows: y = 4 + 2x What does the slope of this function represent? 1) The original height of the plant was 4 mm.
2) The original height of the plant was 2 mm.
3) The height of the plant increases by 2 mm for every hour of sunlight it receives.
4) The height of the plant increases by 4 mm for every hour of sunlight it receives.