What characteristic distinguishes a mortar from conventional firearms?

The ability to fire at a steep angle is a key characteristic that distinguishes mortars from conventional firearms. Mortars are designed to launch projectiles at high angles, which allows them to target areas that might be obstructed by terrain or fortifications. This steep trajectory enables mortars to effectively hit targets located behind cover or on elevated ground.

Conventional firearms, on the other hand, typically fire projectiles at lower angles, focusing more on direct line-of-sight engagement. The steep angle of fire with mortars contributes to their unique tactical application on the battlefield, as they can deliver indirect fire over obstacles and into locations that direct fire weapons may not effectively reach. This capability is crucial for providing support to ground forces in various combat scenarios.

In comparison, the other options, such as the ability to fire only explosive rounds, a higher rate of fire, and the use of large caliber ammunition, do not uniquely identify mortars. Firearms can also be used to fire explosive rounds, and while mortars may have a distinctive firing rate and caliber size, these features are not exclusive to them. The steep angle of firing, however, is a defining operational characteristic that truly sets mortars apart.