Final answer:
The question relates to the physics of structure and force, particularly how much horizontal force a warning line needs to resist to prevent tipping over. Without further context, it is impossible to accurately determine from the given options.
Step-by-step explanation:
The question seems to be related to the stability and strength of a system under horizontal loads. The specific details provided (2.50 N, half a pound of force per 100 m of wire, tensions in wires, bending poles, and shear force considerations) relate to physics concepts such as tensile strength, force, and structural integrity. Unfortunately, none of the given references directly provide an answer about the resistance required for a warning line when tested by a horizontal push. However, it can be inferred that the question deals with understanding the forces acting on structures and their responses. Since all the options are expressed in pounds, it is likely that the student is asking about the amount of horizontal force (in pounds) a warning line needs to resist to prevent tipping over. Without additional context or reference to a specific standard, code, or task-related detail, it is unfeasible to accurately choose between the provided options of 50 lbs, 75 lbs, 100 lbs, or 150 lbs.