Answer:
Independent variable: Adding/not adding soil.
Dependent variables: Does the plant grow? Amount of leaves, plant length.
Controlled variables: Type of plant used, amount of sunlight received, pot used for plant, amount of water given, temperature of soil, etc.
Step-by-step explanation:
Independent variable: The thing that you want to change. To see if plants need soil to grow, you would need to either add or remove soil altogether.
Dependent variables: The thing that is being measured. By adding your independent variable, you should be able to answer certain questions.
Controlled variables: Things you want to keep the same for each experimental group. For example, if you used different plants, your results could be affected negatively as some plants might rely on soil less than others/grow at a slower or faster pace.