The answer to this is C. Industry. It's the only man made factor.
Its called osmosis and it only happens with water. now I'm just adding words to be able to post this. its moving down the concentration gradient.
The earth was once formed by molten layers of the earth and over time layers began to form due to the relative melting points. hope this helps :D
Caleb’s immune system will have the experience of getting rid of this antigen and know exactly what to do to overcome it efficiently.