What must be provided to protect against overflow from CNG cylinders?

Answer: B — diversion curb

To effectively protect against overflow from CNG cylinders, a diversion curb is essential. This feature acts as a barrier that directs any potential leakage or overflow away from sensitive areas, ensuring that gas does not escape into places where it might pose a risk or hazard. By containing the overflow, the diversion curb helps to maintain safety standards and minimizes the potential for accidents or environmental damage. While containment basins and automatic shutoff valves also play important roles in safety, they serve slightly different purposes. Containment basins are designed to hold leaks and spills, while automatic shutoff valves can stop the flow of gas in an emergency. Regular inspection is crucial for identifying potential issues before they lead to a problem but does not actively manage an overflow situation in real-time. Thus, the diversion curb is specifically aimed at managing and directing any overflow, making it the most suitable answer for this scenario.