This is for ESS(Earth Space Science
You are a palaeontologist studying a rock formation with two rock layers next to each other that are noticeably different in their compositions. The difference between the layers suggests that a mass extinction event occurred between them. The following table shows the number of fossils of each group found per layer.
What conclusions can you draw?

1. The number of fossils of amphibians and marine organisms is particularly reduced in layer B. Therefore, layer A probably formed before the Late Devonian extinction and layer B after.

2. Dinosaur and mammal fossils are present in layer B but not in layer A. Therefore, layer A probably formed before the Permian-Triassic extinction and layer B after.

3. Dinosaur and mammal fossils are present in layer A but not in layer B. Therefore, layer A probably formed before the Late Devonian extinction and layer B after.

4. The number of fossils of amphibians and marine organisms is particularly reduced in layer A. Therefore, layer A probably formed before the Permian-Triassic extinction and layer B after.