Older fossils appear in rock layers–below below new new fossilsfossilsabove above new new fossilsfossilsin the the same same layer layer as as new new fossilsfossilsthat that also also have have new new fossilsfossils

below new fossils

Explanation:

Rocks are usually arranged in Layers of which the oldest  are found in the bottom and the recent rock layers found on the top. This is in line with the  Law of superposition which states that every rock layer is older than the one which lies above it, This law together with the Law of faunal / fossil succession helps us to understand the assemblage of fossils and how they succeed each other with time.  From this, we can say that older fossils in a rock will lie farther below a rock layer leading to the oldest fossils occurring at the deepest part of the rock layers and the newest fossils appearing  at the top of rock Layers.

We can therefore say that Older fossils appear in rock layers–below new  fossils.

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

a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.