What type of firearm requires the hammer to be cocked before it can be fired?

The correct answer is single-action. This type of firearm is designed so that the hammer must be manually cocked before each shot can be fired. In a single-action firearm, pulling the trigger does not automatically cock the hammer; instead, it only releases it to strike the firing pin and discharge the round. This mechanism requires the shooter to prepare the firearm for each shot manually, which can result in increased accuracy if the shooter is trained, but it also means that the weapon must be prepared to fire each time.

In contrast, double-action firearms can fire without the need to manually cock the hammer because pulling the trigger performs both actions: cocking and releasing the hammer. Semi-automatic firearms, while they do allow for rapid firing of multiple rounds, also do not require manual cocking after the first shot, as they automatically chamber the next round. Automatic firearms continuously cycle and can fire repeatedly with a single pull of the trigger, eliminating the need for cocking entirely. Thus, understanding the operational mechanisms of different types of firearms elucidates why single-action is the answer to this question.