Final answer:
The length of a safety fuse for blasting can vary depending on local regulations and job safety requirements, but under U.S. federal guidelines, it's typically required to be at least 30 inches long. Since the question's options are in meters, it's important to check specific local regulations for the correct answer.
Step-by-step explanation:
The length of the safety fuse used for blasting is a critical safety consideration in engineering applications, particularly in mining and construction where explosives are used. There isn't a one-size-fits-all answer to this question as it can vary by jurisdiction and specific job safety requirements. However, in many cases, such as under U.S. federal regulations, a non-electric fuse (safety fuse) must be at least 30 inches or 76 centimeters in length to ensure that blasters have sufficient time to reach safety after lighting the fuse and before the explosion occurs. This may not directly translate to the options provided (10m, 20m, 30m, 40m), so it's important to consult specific local regulations or standard operating procedures that apply to the location and type of blasting operation being conducted.