The Coriolis Effect is the influence of Earth's rotation on the direction of winds and currents.

• A. The chemical composition of air
• B. The amount of water vapor
• C. The formation of clouds
• D. The direction of winds and currents

Answer: (D)

The key idea is that moving air and water are curved by Earth’s rotation, so their paths aren’t straight. This deflection, known as the Coriolis effect, causes winds and currents to bend: to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. That turning shapes large-scale wind patterns and ocean circulations, helping explain why trade winds, westerlies, and gyres form, and why storms spin in characteristic directions.

This effect isn’t about what air is made of, how much water vapor it contains, or how clouds form. Those depend on temperature, moisture, and condensation, not the rotation itself. So the description that the Coriolis effect changes the direction of winds and currents matches the concept and is the best choice.