The answer is C :
It controls the entry and exit of substances.
I believe it was James Hutton
In nuclear fission heavier elements are split to make lighter elements whilst releasing energy. An atom, its nucleus to be more specific, is bombarded with neutrons. The nucleus becomes unstable and it starts to split/decay. It creates the fusion products. Neutrons and lighter elements are released; the neutrons from the nuclei of the atom(s) being split.
When magnesium is burned, it reacts with oxygen in air not with the fire. The fire is the energy needed for the reaction to happen. Magnesium reacts with oxygen forming magnesium oxide. The light emitted from the reaction is because the reaction produced a lot of heat.
The reaction will generally form more reactants than products.
