Why does West Africa support a wide variety of ways of life?
A The coastal area has one of the largest
cities in the world.
B The varied geography causes very
different climates.
C The countries of the interior are mostly
covered by desert.
D Human activity has altered the environment
in some places.

B I think

Explanation:

it’s lava came from an explosive eruption

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).