Why do scientists find different fossils in different rock layers?

Three concepts are important in the study and use of fossils: (1) Fossils represent the remains of once-living organisms. ... (3) The kinds of fossils found in rocks of different ages differ because life on Earth has changed through time. Stratigraphic ranges and origins of some major groups of animals and plants.

Explanation:

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well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."

a and c are the answeres