What is the correct action while turning at a curve?

Releasing the clutch pedal while turning at a curve is the correct action because it allows for smoother control of the vehicle. When negotiating a curve, especially in a manual transmission car, it's essential to ensure that the engine remains engaged in the right rev range to maintain traction and control.

If the clutch is engaged properly, it allows the driver to manage the vehicle speed and power more effectively during the turn. This can be critical, as turning with the clutch engaged can lead to stalling or loss of control, particularly if the vehicle is driven in too low a gear or if the driver incorrectly manages the throttle.

Other choices involve actions that could compromise vehicle stability or control. Braking hard can cause loss of traction, making it difficult to steer. Accelerating rapidly while in a curve can lead to understeering or losing grip, while shifting to a higher gear could hinder acceleration and power transmission needed for a smooth turn. Thus, releasing the clutch helps keep the vehicle balanced and manageable through a turn.