A system is designed to generate multiple candidate responses to a prompt and then select the best one. For the prompt 'Describe the primary function of a car's engine,' the system generates the two sets of candidates below.

Set A:

1. The engine's main job is to convert fuel into motion.
2. The principal role of an engine is transforming fuel into mechanical energy.
3. An engine's primary purpose is to turn chemical energy from fuel into movement.

Set B:

1. The engine combusts fuel to power the wheels, making the car move.
2. The engine also powers the alternator, which charges the battery and runs the car's electrical systems.
3. The engine's cooling system, including the radiator, must be maintained to prevent overheating.

Which set of candidates, A or B, provides a better basis for the selection system to choose a high-quality, comprehensive response? Justify your reasoning by comparing the characteristics of the two sets.