That would undeniably be letter "B", tides. Tides are distortions in a planets surface caused by the gravitational attraction of another celestial body. On Earth, this distortion occurs in the raising of the Earths oceans on the side closest to the moon and directly opposite, on the Earths other side. While high tide occurs in these two places, low tide is occuring at 90 degree angles to the high tides, because the water that is added to the sides of the Earth to make high tide is taken away from the other locations on Earth. The sun has an effect on the rise and fall of tides on Earth, but it is the moon that is closer, producing the dramatic rise and fall of the ocean waters. When the tides come rolling in, they create all kinds of temporary environments for organisms to live in. These organisms must be able to live both in water, during high tide, and on dry land, during low tide.