Easy just get some water and get a cup and pow
Available oxygen
Available oxygen is the amount of oxygen present at a specific time that can be used in aerobic cellular respiration.
Aerobic cellular respiration is a metabolic process that occurs within the cells of organisms. In this process, oxygen is used in the mitochondria to chemically convert organic molecules such as glucose into adenosine triphosphate (ATP), with the release of water and carbon dioxide as waste products. Aerobic cellular respiration results in a larger amount of energy (ATP) which is used by the cell to perform its activities.
In physical science there are two types of "isolated systems"
1. Being a Physical System in which it is so far removed from other systems that it does not react with any of them.
2. Being a Thermodynamic System in which it is enclosed by rigid immovable walls of which neither mass nor energy can flow through.
I believe in this case although not stated that it would refer to a Thermodynamic System which would leave you with the only plausible answer as ENERGY AND MATTER CANNOT ENTER OR LEAVE.
None of the other answers make sense. Even if it were referring to Physical. Physical does not react with anything at all. An as you can see Thermodynamic does not allow for anything to pass through or leave.
<span>since plants are at the bottom of the food web and provide the most energy</span>
