i think A would be right if they are taking ab the scientific method
You water three sunflower plants with salt water. Each plant receives a different concentration of salt solutions. A fourth plant receives pure water. After a two-week period, the height is measured. i think the indepent variable is sunflower ... variable is height measured and the control variable is the fourth plant.
I’m pretty sure The answer Is D. I did the test not to long ago and I got it all right. :)