Answer:
A. the food web
Explanation:
Ecosystems have lots of different living organisms that interact with each other. The living organisms in an ecosystem can be divided into three categories: producers, consumers and decomposes. They are all important parts of an ecosystem. Producers are the green plants.
25 times with 2 heads, 25 times with two tails, 50 times with one head and one tail.
Oil Coal and Natural Gas are the fossil fuels the USA has the most reserves of. Given that only one of them is on the answers Coal is the correct answer.