In the Hubbard Brook Experimental Forest in New Hampshire, a Portion

In the Hubbard Brook Experimental Forest in New Hampshire, a portion of the forest was first clear-cut, then sprayed with herbicides for 3 years to prevent growth. A second portion of the forest was not clear-cut or sprayed and served as a control plot. The graph below shows that nitrate, a form of nitrogen that is important to plants, was lost from the ecosystem in streams at a much higher rate in the clear-cut portion of the forest than in the control portion.
What best explains the small releases of nitrogen from the control portion of the forest at the Hubbard Brook Experimental Forest?

A) Its nitrogen was sequestered in the forest biomass and temporarily unavailable.
B) With intact vegetation to intercept the acid rain that falls in the area it failed to reach the soil and chemically react to release the nitrogen.
C) With intact vegetation, rainwater washed little soil and nitrogen from the forest floor.
D) All of the above contributed to the small amount of nitrogen loss.