i want to set up an experiment to test how coffee affects Plant growth. Both plants will have the same potting soil, sunlight, plant species, sunlight exposure, an the amount of water each day. One plant will give 100ML of water 3 times a week. The other plant will receive 100ML of water with coffee grounds 3 times a week. I will measure the plant growth every two weeks, what are the CONSTANTS in this scenario- pick all that are correct

Plant height
Soil
Coffee grounds
Water amount
Sunlight
Plant species