ohannes wants to know whether soil, water, or both are needed for plant growth. He chooses to conduct experiments on a willow tree for five years to answer his question. How can his experimental methods be changed to improve his experiment?

She can plant a plant in one pot full of dirt and not water the plant to see if it is neccesary

Then she can plant a plant in a pot of nothing but water and see if the plant grows well

then she can plant a plant in a pot of both adding water to the soil.

In an expiriment you need to change the vairables to see if the results change, and, then reocrd your results.