A or c but I think it is a
Answer:
I think the answer is C. Reduction of atmospheric CO2
Explanation:
I hope this helps! Correct me if I am wrong.
Answer:
1. True
Biotic factors can have effect on abiotic factors like water by the way they use it and how much they drink. If biotic factors drink too much water in a rivver then it could end up with limited amount of water for the ecosystem.
2. False
On average, about 50 percent of energy available within one trophic level is transferred to the next trophic level.
3. True
Extirpation is extinction of a species in a given area.
So to solve this problem, we are going to have to set up a couple unit conversions and then cancel units:

This method can be used to convert between many different units and is a very helpful tool for questions such as these.