Natural Selection is when traits are "naturally" selected for, because "survival of the fitttest." Example would be a species becoming bigger over time, because the smaller animals of that species were more likely to be eaten by predators. Natural selection is when the "best" trats are passed down due to chance
Selective breeding is if an outside forece (like a dog breeder) "chooses" a triat to be passed down. Example, instead of breeding a brown dog with a white dog, the breeder breeds two black dogs together in orer for the litter to all have black fur
The best answer to the question above would be the first statement. Cardiorespiratory endurance affects physical fitness in such a way that it increases the efficiency with which the body delivers oxygen and nutrients to its cells.
