What Best Explains the Differences in Shoot Weight Shown in the Following

What best explains the differences in shoot weight shown in the following graph?

A) Commercial fertilizers often contain harmful contaminants that can suppress growth.
B) Sterilized growth environments remove competitive bacteria and fungi, allowing plants to experience their best possible growth.
C) Commercial fertilizers can be tailored to meet the needs of specific plants, producing the best possible growth for that species.
D) Mycorrhizal fungi not only increase the availability of soil nutrients but often transport them into the plant root.