The oceanic crust cycles. New crust is created at the mid-ocean ridges. The new material is and pushes the older material. As the material spreads outward, it becomesanddense. Eventually, the old oceanic crust hits the continental crust and, forming a . The reason the oceanic crust subducts is because. The crust is then returned to the earth's, heats and cools in currents until one day it will. PLEASE HELP

just here for the other one bc they put up with u

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).

b. lithosphere, asthenosphere, mesosphere   is the answer most likely

c. heat from the poles back down towards the equator.