Which two pyrotechnic devices must ensure their trajectory is not over the audience?

The correct choice emphasizes that both comets and mines are pyrotechnic devices that require careful consideration regarding their trajectories to ensure public safety. Comets, which typically consist of a cylindrical shell with a bright tail, and mines, which are ground-based effects that shoot up and explode, are designed to project material into the air. If these devices were to discharge over an audience, it could result in serious injuries or accidents from the falling debris or explosion.

Ensuring that their trajectory is away from the audience is an essential safety regulation that aligns with NFPA guidelines to minimize risk during displays. This is vital for protecting spectators since both devices can achieve significant heights and can produce loud blasts and bright flashes, which can create a hazardous environment if not properly controlled.

On the other hand, while rockets, fountains, cakes, shells, salutes, and sparklers all have their unique safety considerations, their trajectories may not be as critical to divert from audience areas in the same way as comets and mines. Therefore, understanding the specific behavior and projection characteristics of these two devices underscores the importance of monitoring their paths to maintain a safe viewing experience for all.