The pressure in a fluid is affected by which characteristic of that fluid?

A. The weight of the fluid

B. The gravity of fluid

C. The amount of oxygen atoms in the fluid

D. The amount of hydrogen atoms in the fluid

In a liquid, the pressure comes from the weight of the fluid and the weight of the air above it, which we call the atmosphere. You feel this pressure when you swim under water. The deeper you go, the more pressure you feel. This is because there is more weight pressing down on you from above as you increase your depth. The same principle is true for atmospheric gases. The lower in elevation you are, the more weight and pressure you experience. But even though these gases are constantly putting pressure on you, you don't feel it because your body is the same pressure as the surrounding air. Fish experience the same thing underwater - their bodies are the same pressure as the surrounding fluid, so they don't notice the constant pressure the water exerts.