Final answer:
Improper welding procedure and consistently overloading a trailer are the most likely causes for an upper coupler bolter plate to become distorted into ripples, due to introducing residual stresses and exceeding design capacity respectively. The best choice of options are (A) and (B).
Step-by-step explanation:
Which of the following would be more likely to cause an upper coupler bolter plate to become distorted into ripples? Among the possible causes, improper welding procedure during assembly and a trailer consistently overloaded are likely to be significant factors. Improper welding can introduce high levels of residual stress and weak points that can lead to distortion under stress.
Consistently overloading a trailer can exceed the design capacity of the upper coupler bolter plate, leading to permanent deformation, such as rippling, due to metal fatigue or plastic deformation.
Occasional on/off-road use might contribute to wear and tear over time but is less likely to cause immediate distortion unless the conditions are extremely harsh. Lack of lubrication would more typically cause problems within moving parts such as bearings rather than the bolter plate itself.