Refer to the Figure

Refer to the figure.

-Which statement best explains the downward trend that follows the peak of each curve?

A) Low soil moisture limits the activity of decomposers.
B) Soils with over one half of the water content indicated have concentrations of oxygen that are too low for optimal rates of decomposition.
C) Soils with extremely high water content are unable to sustain decomposition activity.
D) Soils with over one half the water content indicated increases the metabolic rate of decomposers.