Final answer:
A person with impaired spinal rotation is most likely to experience difficulty when trying to look over their shoulder, such as when backing up a car, because this movement heavily relies on spinal rotation.
Step-by-step explanation:
The functional activity that would most likely display dysfunction by a person who had impaired spinal rotation at multiple levels is looking over the shoulder while backing up a car. This movement requires the ability to rotate the spine, and impairment would directly affect the individual's capability to perform this action without experiencing difficulty or discomfort. Activities such as looking upward to see an object on a high shelf, looking downward when tying shoelaces, or looking forward at a computer screen are less dependent on the ability to rotate the spine and would be less affected by this particular type of dysfunction.