What characteristic of an object allows air and water to move through it easily?

The ability of air and water to move through an object easily is closely related to its streamline characteristic. An object that is streamlined has a shape designed to reduce resistance as fluids (like air and water) flow around it. This means that, in a streamlined object, the design allows for smooth and efficient movement of fluids, minimizing turbulence and drag.

When considering other characteristics, while density refers to how heavy or compact an object is, it does not directly relate to the movement of air and water through the object. Similarly, rough surfaces create friction that can impede flow, while opacity deals with how much light can pass through an object, which is also unrelated to the movement of fluids. Therefore, the streamlined shape is what specifically enables easier passage of air and water.