What does the "shell casing" of a mortar round contain?

The shell casing of a mortar round is designed primarily to house and protect the explosive charge and the fuze mechanism. The casing provides structural integrity to withstand the forces experienced during firing and impacts. The explosive charge is the material that detonates upon impact or when triggered by the fuze, while the fuze is responsible for initiating the explosion at the right moment, either upon impact or after a predetermined time.

The other options, while related to ammunition in general, do not accurately describe the primary contents of a mortar shell casing. The focus on explosives and the fuze mechanism is key to understanding the purpose of the shell casing in mortar rounds, as it is crucial for both the effectiveness and safety of the ammunition during operation.