Answer: Option B
Explanation:
Usually in scientific experiments, at least one parameter is checked; here, the growth rate of wheat in two different conditions is being evaluated.
Hence, growth rate of wheat alone in pans A, B and C becomes the standard or referential control against which the experimental control (Wheat + clover) in pans D, E and F is evaluated, since both treatments are exposed to the same external conditions.
I hope this helps
Most enzymes end with the suffix -ase. Example: ligase, protase, maltase, Of course there are few exceptions like pepsin.