when scientists first studied electromagnetic energy, many theories were proposed to explain how these waves travel through space. which statement below best describes how scientists arrived at the current understanding of electromagnetic energy?

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Explain how you might determine the rate of weathering on a sample rock

In the image, layer a is the topmost layer. layer c contains fossils from the precambrian era. layer b contains dinosaur fossils, and layer a contains fossils of mammals. which two statements are supported by this evidence? 1. mammals lived before the precambrian era. 2. dinosaurs and mammals existed in the precambrian era. 3. dinosaurs evolved after precambrian organisms. 4. precambrian organisms evolved after dinosaurs. 5. precambrian organisms were the first life-forms to become fossilized, according to this sample.