As scientists search the universe for signs of like on other planets they are likely to focus on the presence of molecules containing which of the following elements? a) carbon b) calcium c) iron d) magnesium

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