The correct answer is option 4: Pressure gradient force.

Gravitational force (option 1) is not the most powerful force in determining the movement of wind. Although it does play a role in the overall circulation of the atmosphere, its effect on wind movement is relatively small compared to other forces.

Centrifugal force (option 2) is also not the most powerful force in determining wind movement. While it is responsible for the curved shape of wind patterns in cyclones and anticyclones, it does not directly drive the movement or velocity of the wind.

Frictional force (option 3) is an important force in slowing down the wind near the Earth`s surface, but it does not determine the overall movement of wind.

The pressure gradient force (option 4) is the most powerful force in determining the movement of wind, including its velocity. It is caused by differences in air pressure between two points, and air moves from higher to lower pressure areas. The greater the pressure difference, the stronger the force, and the faster the wind will blow. Therefore, the pressure gradient force is the primary force driving wind movement in the atmosphere.