Question

what can fossils found in rock layers tell scientists?
the size of earth
which living things existed and when they lived
how old the oceans are
the location of volcanoes

Explanation:

Fossils are the remains or traces of ancient organisms. Rock layers (strata) are formed over time. By studying the fossils in different rock layers, scientists can determine which organisms existed (as the fossils are of those organisms) and when they lived (since each rock layer represents a different time period in Earth's history). The size of the Earth is determined through geological and astronomical measurements (not fossils), the age of the oceans is calculated using radiometric dating and other geochemical methods (not primarily from fossils in rock layers), and the location of volcanoes is related to tectonic plate activity (mapped through geological surveys, not from fossils in rock layers).

Answer:

Which living things existed and when they lived