Answer:
Independent Variable: Type of fertiliser
Dependent Variable: Height of plant
Controlled Variables: Location of plant, volume of water, soil pH, amount of fertiliser, type of plant
Control: No fertiliser plant
Step-by-step explanation:
Independent variables are the one thing in the experiment that we change to test someting. In this case, we are changing the type of fertiliser used to test which type of fertiliser is best for maximum plant growth.
Dependent variables are thing that is being measured in the experiment. In this experiment, we are measuring the height or growth of the plant.
Controlled variables (I assume this is what you call a constant) are the things that stay the same to ensure the experiment is valid and is a fair test.
Controls are something that the independent variable is not applied to, often used to compare the results of those that are influenced by the independent variable. In this experiment, we can use a control which is a plant that is not given any fertiliser. The height of this plant can then be compared to those given fertiliser to see if fertiliser can actually make a plant grow taller or not have an effect at all.