A. Soil environments aren't affected by nutrient limitation. False
Soil can have limited nutrients if particular type of crop is grown continuously. That's why different crops are grown in different seasons. Also, fertilizers and manures are added with then aim to replenish the nutrients.
B. Limiting nutrients are the nutrients whose supply is in excess. False
If then nutrients were provided in excess quantity, then they will not control the productivity. Thus this statement is false.
C. If one essential nutrient within an ecosystem runs out, primary productivity will be limited. TRUE
Essential nutrient controls the growth of the plant. Therefore, it will regulate the productivity as well.
D. Nitrogen is typically the limiting nutrient in freshwater environments. False
It is not a limiting nutrient.
So the answer is C. Nitrogen is typically the limiting nutrient in freshwater environments.
This is because Nitrogen is the "scarce" nutrient