One key adaptation of animals was the evolution of a(n) , a fluid-filled gap between the outer wall of the body and the outer wall of the digestive system.

Dr. arenas is a scientist who has been trying to determine if increasing pressure will increase the sound that occurs when two chemicals explode. it measures the volume of the sound that occurs at the minimum pressure at which the explosion will occur. it then increases the pressure and measures the volume of the explosions that occur. what kind of investigation is the scientist conducting?