Which words correctly complete: The Polar cell is thermally ____; Cold air ____ at the North Pole, before flowing south at the surface.

Which words correctly complete: The Polar cell is thermally ____; Cold air ____ at the North Pole, before flowing south at the surface.

• A. Direct; Sinks
• B. Direct; Rises
• C. Indirect; Sinks
• D. Indirect; Rises

Answer: (A)

The Polar cell is thermally direct because its circulation is driven by temperature contrasts: very cold air at the poles cools and sinks, creating a surface high, and air from these cooler regions moves toward lower latitudes at the surface to replace the sinking air. At the North Pole, the air is so cold and dense that it tends to sink, forming subsidence there, and this sinking air then flows southward at the surface to complete the cell. Rising occurs farther from the pole where colder polar air meets warmer mid-latitude air, allowing air to lift aloft before returning poleward. So the sentence correctly completes as thermally direct; Cold air sinks at the North Pole, before flowing south at the surface.

The Polar cell is thermally direct because its circulation is driven by temperature contrasts: very cold air at the poles cools and sinks, creating a surface high, and air from these cooler regions moves toward lower latitudes at the surface to replace the sinking air. At the North Pole, the air is so cold and dense that it tends to sink, forming subsidence there, and this sinking air then flows southward at the surface to complete the cell. Rising occurs farther from the pole where colder polar air meets warmer mid-latitude air, allowing air to lift aloft before returning poleward. So the sentence correctly completes as thermally direct; Cold air sinks at the North Pole, before flowing south at the surface.