Answer:
A) Soils rich in humus improve plant growth.
Step-by-step explanation:
Humus improves the organic matter content in the soil, so the soil has the ability to provide plants with a malleable soil, rich in nutrients and with a vast and healthy population of microorganisms. All of this allows plants to grow less and their production capacity to be stimulated.
Well based on that and based on the results of the experiment shown above, we can say that soils rich in humus improve plant growth.