What should a driver do if they notice cracks in their brake drums?

Answer: C — Immediately replace or repair them

When a driver notices cracks in their brake drums, immediately replacing or repairing them is crucial for maintaining vehicle safety. Brake drums are essential components of the air brake system, and any compromise in their integrity can significantly affect braking performance. Cracks can indicate potential failures that could lead to brake failure, which poses a serious risk both to the driver and other road users. Addressing the issue promptly ensures that the vehicle remains safe to operate. This proactive approach not only adheres to safety regulations but also prevents more extensive damage and potentially costly repairs down the line. In the context of vehicle maintenance, prioritizing the integrity of the brake system is essential for safe driving practices, which is why immediate action is the correct response when defects like cracks are observed.