Explanation:

- Coriolis Force (Option 4):

- The Foucault pendulum's plane of oscillation rotates due to the Coriolis force.

- It results from Earth's rotation, affecting the pendulum's path.

- This force causes the pendulum to appear to rotate, demonstrating Earth's rotation.

- This is the correct option.

- Centripetal Force (Option 1):

- Acts towards the center of a circular path, maintaining circular motion.

- It doesn't cause rotation of the oscillation plane of the pendulum.

- Viscous Drag of Air (Option 2):

- This is the resistance from air on the pendulum's motion.

- Affects the pendulum's speed but not the rotation of its oscillation plane.

- Centrifugal Force (Option 3):

- An apparent force experienced in a rotating reference frame.

- It doesn't influence the plane of oscillation directly for the pendulum.