Diffusion happens when there is a difference in concentration. So for water to diffuse out of the cell, the concentration of water has to be lower outside the cell, than inside the cell.
Newton realized that the reason the planets orbit the Sun is related to why objects fall to Earth when we drop them. The Sun's gravity pulls on the planets, just as Earth's gravity pulls down anything that is not held up by some other force andkeeps you and me on the ground.
Pretty sure answer is the last one... soil, habitats, water and air quality...sorry if im wrong
By using a skin graft they are protecting the area of the burn from getting infected.