Which of the following is an example of an ecosystem? A. an oyster
B. a school of fish
C. fish and sharks
D. the open ocean

D. the open ocean

Explanation:

The reason why I cannot be any of the other answers are because, A is just a single organism which would in fact be incorrect. A school of fish would be incorrect because, it only includes a bunch of the same fish. The Ecosystem (As it says in the capture below) is a bunch of different organisms that work together like a shark might eat the fish but, that is about it. The entire ocean is a great example of a ecosystem because, there are all kinds of things that create the ecosystem. Therefore, your answer could only be D. the open ocean.

Information in the picture below:

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.