Johannes 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?

He could conduct multiple experiments at same time. For example, he can grow one willow tree in just water, one in just soil, and one tree in combination of soil and water. Then after a certain time, say 5 years, he can see their growth and determine what's the best approach for plant growth.

Explanation:

where is the option.let me know

the darker peppered moth species were favored due to the fact that the industrial revolution had made all the nearby trees a darker color instead of white.