Final answer:
The term for a long commercial vehicle's tendency to swing wide on turns is offtracking. The correct option is b).
Step-by-step explanation:
The correct term for a long commercial vehicle's tendency to swing wide on turns is b) Offtracking. This occurs when the rear wheels follow a different, usually tighter path than the front wheels when the vehicle goes through a curve or makes a turn. This is especially noticeable in vehicles with trailers.
Like semi-trucks or freight trucks, due to their long wheelbases and the pivot point between the truck and the trailer. Regarding the observation of a trailer bouncing up and down slowly on the highway, it is more likely that the trailer is nearly empty.
A heavily loaded trailer would typically have less bounce because the weight stabilizes the movement, while an empty or lightly loaded trailer is more susceptible to bouncing due to less weight to dampen the bouncing motion caused by road imperfections or air turbulence.