Natural selection<span> is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations.</span>
Amphibia is the class of vertebrates which is considered to be the first to develop lungs. This allowed amphibians to live successfully on land as terrestrial organisms. Ichthyostega was the first primitive amphibians with nostrils and lungs. Amphibians adopted themselves to live on land with developed lungs.
The solar system is considered a natural system because it was made and controlled by natural forces, meaning, it was never influenced with human creations. It is considered as one of the products of the phenomenon of the physical world. Hope this answer helps you.
The answer is d. atmosphere < leaves < roots < soil
