The main form is carbon dioxide and methane
<span>"D.how living things are interconnected with their environment</span>" is the correct answer. Ecology has to do with systems of environments as a whole, and the organisms that live there.
NaCl is dissolved in water so that in a given region or volume the concentration is initially higher in one part than the other l, thus simple diffusion will occur so that there is a net difference or 0, with respect to the concentration of NaCl in a particular volume of water than another. Basically the NaCl will be distributed throughout volume of water.