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.
Correct answer: D). Energy and matter cannot enter or leave.
An isolated system is a system in which neither the energy nor the matter can enter or leave the system. As a result of that, the total mass of the system remains unchanged.
There is a change in the species present, But, the total mass present will not change based on the law of conservation of matter and energy.
Plants make their food in their leaves. And need sun for this process, so smaller and fewer leaves means less sun for photosynthesis, and it also means less food to nourish the plant.