I would say C.nervous system because that pretty much defines all of the answer choices.
The inner planets are those that orbit closer to the sun: mercury, venus, earth and mars.
Attending to the size this is the increasing order: mercury, mars, venus and earth.
Earth is the largest of the inner plantes.
(1) they keep toxic substances out of the cell;
(2) they contain receptors and channels that allow specific molecules, such as ions, nutrients, wastes, and metabolic products, that mediate cellular and extracellular activities to pass between organelles and between the cell and the outside environment;
(3) they separate vital but incompatible metabolic processes conducted within organelles.
I think it would be Ionic Solution
