In artificial selection, humans provide the selective pressure for species to change and shape the evolution of various breeds. what provides the selective pressure in natural selection?
a) the environment
b) the degree of natural genetic variation in a population
c) disease
d)scientifically trained humans

a) The environment.

Explanation: Natural selection is one of the forces of evolution. Natural selection occurs when individuals in a population have a different reproductive success in certain environment. For example, imagine a mosquitoes population in a insecticide-free envrionment, the non-resistent mosquitoes will be more succesfull that the resistant ones. But when there's insecticide in the environment, the resistent mosquitoes will be more successfull that the non-resistent ones, because they die.

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