Which of the following is a true statement regarding mineral nutrients in soils and their implication for primary productivity?

A) Globally, phosphorous availability is most limiting to primary productivity.
B) Adding a nonlimiting nutrient will stimulate primary productivity.
C) Adding more of a limiting nutrient will increase primary productivity, indefinitely.
D) Phosphorous is sometimes unavailable to producers due to leaching.
E) Alkaline soils are more productive than acidic soils.