Which of the following are types of semiautomatic firearms?

Semiautomatic firearms are those that fire one round each time the trigger is pulled and automatically cycle the action to load the next round into the chamber from the magazine. The correct choice encompasses various mechanisms commonly found in semiautomatics, including single action, double action, and striker-fire systems.

Single action firearms require the hammer to be cocked before the trigger is pulled to fire, while double action firearms allow the trigger pull to both cock the hammer and fire the weapon. Striker-fire systems, prevalent in many modern handguns, eliminate the external hammer altogether and use an internal mechanism to fire the round. Each of these mechanisms represents a valid method by which semiautomatic actions operate.

The other options do not fully represent the types of semiautomatic firearms. For instance, revolvers are typically classified as manual-action firearms and not semiautomatic, while bolt-action mechanisms are associated with rifles that require manual cycling of the action. Lever actions are also not semiautomatic; they are manually operated firearms. Therefore, the recognition of single action, double action, and striker fire as commonly associated with semiautomatics illustrates the correct understanding of the diverse functioning mechanisms within this category of firearms.