The only consumables that is not digested and is immediately absorbed, would be water, it is nothing but a polar compound that does not yield as much energy as all of the other molecules.
Watersheds are important because the surface water features and stormwater runoff within a watershed ultimately drain to other bodies of water. It is essential to consider these downstream impacts when developing and implementing water quality protection and restoration actions. Everything upstream ends up downstream.
B. atmosphere since the atmosphere is made up of o2, co2 (a greenhouse gas) and nitrogen. those are the primary elements
