A burning safety fuse burns in what way?

• A. It bursts into flame and sparks
• B. It burns internally with some smoke and a little melting behind the point of burning; it doesn't show flame or spark as it burns and it should not jump
• C. It immediately ignites explosives
• D. It produces continuous flame

Answer: (B)

The concept here is how a safety fuse behaves when it’s burning. A safety fuse is designed to burn quietly along its length, not with an open surface flame. You’ll typically see some smoke and a little melting just behind the point where the fuse is burning, as the heat progresses inward along the fuse. There should be no visible flame or sparks at the surface during normal burning, and the burn should move along the fuse rather than jumping ahead or flashing to nearby explosives. This controlled, inward burn lets the delay mechanism do its job without prematurely igniting the charges.

That’s why the description of burning internally with some smoke and a little melting behind the burning point, without flame or sparks and without jumping, is the correct behavior. If a fuse produced a continuous surface flame, sparks, or instantly ignited explosives, those would indicate improper or unsafe behavior for a safety fuse.