a student has samples of two pure compounds, xclo3 and zclo3, which contain unknown alkali metals x and z. the student measures the mass of each sample and then strongly heats the samples to drive off all the oxygen, leaving solid residues of xcl and zcl. the student measures the mass of the solid residue from each sample. which of the following questions can be answered from the results of the experiment?

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.