Explanation:

- Option 1: Pressure Gradient

- The pressure gradient is a key factor in determining wind velocity. Winds blow from high pressure to low pressure areas.

- This movement is driven by the difference in atmospheric pressure.

- Option 2: Pressure Gradient and Humidity

- While pressure gradient affects wind speed, humidity primarily impacts weather conditions, not wind velocity.

- Option 3: Coriolis Effect

- The Coriolis effect influences the direction of winds, not their speed. It causes winds to deflect due to Earth's rotation.

- Option 4: Pressure and Earth’s Rotation

- Wind velocity is influenced by pressure gradients, with Earth's rotation affecting wind direction via the Coriolis effect.

Correct Answer:

- The combination of pressure and Earth’s rotation affects wind velocity. So, Option 4 is appropriate.