The main mechanism through which the layering happened is gravity: it pulled the heavier, denser material to the center, leaving the less dense material on the surface.
The material that was on the outside cooled quicker, but this was the result, not the cause.
The answer is
<span>2) Gravity caused more-dense material to move toward the center of each planet.</span>
This is known as the visible spectrum of electromagnetic radiation, or visible light. This is the frequency of light that we see, and which illuminates our world as it reflects off of objects. Compared to the full spectrum of electromagnetic radiation, the visible light portion is actually quite small.
The correct answer is - A. Devonian.
The Devonian is one of the seven periods of the Paleozoic Era. It lasted for 50 million years, from 410 million years ago until 360 million years ago. It is the period in which the first insects evolved, the first seeded plants, as well as the first land vertebrates. This period came after the Silurian period, and was followed by the Mississippian period.
A since they must have evolved for a common ancestor or they would have different bone structure
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