The answer is Mitochondria
Hope that helps! :)
I think the answer is nitrogen fixation.
The correct answer is this: IT BECOMES LESS DENSE AND RISES TO THE SURFACE.
The water at the earth's poles are cold and dense. This cold water sink and move along the ocean floor in a current. As it moves towards the equator, the cold water from the poles push up the warmer water, this becomes less dense and rise to the surface.
