Answer is c. If one essential nutrient within an ecosystem runs out, primary productivity will be limited
According to Vitousek et al., 2010, nutrient limitation defined as meaningful additions of an essential element in biologically available forms which increases the rate of primary productivity or increase in the biomass in an ecosystem. Alternately, nutrient limitation may also explained as when the supply of one essential nutrient of the ecosystem runs out the primary productivity of the plants will be limited.
There were more dark moths around factories because trees were darker near factories because of pollution. More light moths were found in the country away from the factories, in the forests with no factory pollution
