What could happen if the safety valve fails to operate correctly?

The choice indicating that pressure may exceed safe limits and cause failure is correct because the safety valve is a critical component designed to prevent excessive pressure build-up in a boiler. If the safety valve fails to operate correctly, it may not release steam or pressure as intended. This malfunction can result in dangerously high pressure levels within the boiler, potentially leading to catastrophic failure or even explosions. The safety valve is there to ensure that the pressure remains within safe operational limits, and if it does not function properly, it undermines the safety mechanisms of the boiler system.

In contrast, the other options do not accurately reflect the consequences of a safety valve's failure. The assertion that the boiler may become more efficient is misleading, as inefficiency is a likely outcome of such a failure due to the risk of operating under unsafe conditions. The potential drop in the water level below the Normal Operating Water Level (NOWL) is related to water level controls, not directly tied to the safety valve's operation. Lastly, while there may be automatic shutdown mechanisms in certain boiler systems, they are not guaranteed responses to safety valve failures, especially if the failure occurs unexpectedly. Thus, choice B correctly identifies the serious risk posed by a malfunctioning safety valve.