In an experiment to test the hypothesis that added phosphate will cause marigolds to produce more blooms, the experimenter has two groups of pots planted with marigold seeds. One group gets watered with phosphate added to the water, while the other group gets watered with no phosphate. Both groups get the same amount of water and light.
Which is the independent variable in this experiment?
A. amount of light
B. amount of water
C. amount of phosphate
D. amount of blooms on a plant
