Which of the following are key components of a shell casing?

The answer is accurate because the key components of a shell casing are indeed the projectile, fuse, propellant, and driving band.

The projectile is the part of the ammunition that is propelled out of the barrel when the firearm is discharged. The fuse is a critical component that ignites the propellant; this part ensures that the ammunition fires at the right moment. The propellant is the chemical substance that burns rapidly, generating gas and pressure to propel the projectile down the barrel. The driving band is a feature on the projectile that engages the rifling in the barrel, ensuring proper spin and accuracy during flight.

Understanding these components is crucial for grasping how ammunition functions within firearms and the overall mechanics of shooting. The other answer choices introduce terms that do not correctly describe the components of a shell casing in ammunition.