What feature allows a semi-automatic handgun to automatically load a new round after firing?

The feature that allows a semi-automatic handgun to automatically load a new round after firing is the slide. When a round is fired, the energy generated by the firing process operates the slide, causing it to move rearward. This movement ejects the spent cartridge casing and simultaneously compresses the recoil spring. As the slide moves forward again, it strips a fresh round from the magazine and chambers it, ensuring that the handgun is ready to fire again with minimal intervention from the shooter.

In contrast, the trigger is the mechanism that releases the firing pin to ignite the cartridge but does not contribute to the loading of a new round. The magazine holds the ammunition but does not have an active role in the process of loading a round; it simply supplies rounds to the firearm. The safety is a feature designed to prevent accidental discharges and does not play a role in the loading mechanism of the handgun.