I believe it's b but I may be wrong
What are the options for the question?
Answer:
Aumento del costo de los servicios con tendencia al colapso. - Aumento de los impuesto y del coste de la vida en general. - Descenso de la calidad de vida
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>
<span>Erosion by rivers is a main valley-forming
process; other processes, such as movement of the earth's crust and
glaciers, also have an important part in some cases. The rate at which a
river deepens its valley depends on several factors.</span>
