What percentage of cars in a train must have operative brakes?

The requirement that 95 percent of cars in a train must have operative brakes ensures a high standard of safety and operational efficiency. This percentage is established to guarantee that the majority of the train's cars can effectively slow down, stop, or hold the train as needed, particularly in emergency situations.

Maintaining such a standard is crucial for both the safety of train operations and for minimizing the risk of accidents. With a 95 percent requirement, even if a small number of cars are found to have malfunctioning brakes, the train will still have a sufficient braking capability to operate safely. This measure also reflects industry practices aimed at consistently maintaining high safety standards.

The other possible percentages do not align with the stringent requirements set forth to ensure the safe operation of trains, making the 95 percent threshold the correct answer.