The evidence it leaves is what type of environment it was then, how big were the animals, who ate what, and etc. it can draw conclusions of what animals were then and how animals have went through evolution. Scientists are able to make hypothesis and educated guesses on things.
Methane is the gas that is strongly correlated with Earth's heating and cooling patterns. Did you know that cow's flatulence is methane gas?! Interesting fact!
The receptor is the sensing component that monitors and responds to changes in the environment, either external or internal. Receptors include thermoreceptors, and mechanoreceptors.
The answer is A. Electron transport chain because of ATP synthase which is apart of the ETC and produces the majority of the ATP produced in cellular respiration.
