If f(x) is the height, in cm, of a sunflower plant which is x days old, which of the following statements best describes the meaning of f(60) = 210? . a) the height of the sunflower plant is 60 cm when it is 210 days old. b) the height of the sunflower plant is 210 cm when it is 60 days old. c) the height of the sunflower plant is 210 cm when it is 3.5 days old. d) the height of the sunflower plant is 60 cm when it is 3.5 days old.