Final answer:
The setting of a fusible plug refers to the temperature at which it is designed to melt or rupture.
Step-by-step explanation:
The setting of a fusible plug refers to the temperature at which it is designed to melt or rupture. It is typically used as a safety device in boilers and pressure vessels to prevent catastrophic failure. In this case, the correct answer is (B) 300° F, as indicated by the options given. When the temperature reaches 300° F, the fusible plug will melt, releasing pressure and preventing any potential explosion. The setting of a fusible plug is typically specified as a temperature. Fusible plugs are designed to melt at a certain temperature as a safety mechanism to prevent excessive pressure buildup—this is usually relevant to steam boilers and pressurized systems. The correct option for the setting of a fusible plug is not provided in your question, as fusible plugs are rated by temperature, usually in degrees Fahrenheit or Celsius, and the actual temperature setting can vary depending on its application and the manufacturer's specifications.