Which mortar fuse is used for near-surface burst detonation?

The correct choice for a mortar fuse used for near-surface burst detonation is indeed the NSB fuse, which stands for Near Surface Burst. This fuse is specifically designed to detonate munitions just above the ground or at shallow depths when the round is fired at a target close to the earth's surface. The effect of a near-surface burst maximizes the blast and fragmentation effects, making it particularly effective against personnel and light material targets.

In contrast, the other options serve different functions. The IMP fuse is typically used for impact detonation, ensuring that the round explodes upon hitting a solid target. The DLY fuse is designed for delayed detonation, which allows the round to penetrate before exploding, useful against fortified structures or armored targets. The PRX fuse refers to a proximity fuse, which detonates when it comes within a certain distance of the target, effective for aerial munitions or scenarios where precision timing is not critical but height above ground is.

Overall, the NSB fuse uniquely fulfills the requirement for near-surface detonation, maximizing the effectiveness of mortar rounds in close engagement scenarios.