Stiffness in the neck can make it difficult for drivers to______.

Stiffness in the neck significantly impacts a driver's ability to perform head movements that are essential for safe driving. When a driver has a stiff neck, their range of motion is limited, particularly in turning their head to one side or the other. This is crucial when checking blind spots, as it involves looking over the shoulder to ensure there are no vehicles or pedestrians that are not visible in the mirrors.

In scenarios where a driver needs to change lanes or make a turn, the inability to turn the head can lead to unsafe driving conditions, increasing the risk of collisions. This limitation can hinder overall situational awareness on the road, making it imperative that drivers maintain flexibility in their neck to drive safely. The other options, while also important aspects of driving, do not directly relate to the specific mobility issue presented by a stiff neck in the context of checking blind spots.