What device helps prevent accidental firing in firearms?

The correct answer highlights the role of a safety mechanism in firearms, which is designed specifically to prevent accidental discharges. The safety is a mechanism that blocks the firing pin or prevents the trigger from being pulled without intentional engagement. This feature is essential for ensuring that the firearm cannot be discharged unless the user deliberately disengages the safety, which acts as a critical layer of protection, especially when handling or transporting firearms.

While other devices listed, such as a bolt handle, trigger guard, and sight, play important roles in the operation and handling of a firearm, they do not directly prevent accidental firing. The bolt handle is essential for chambering ammunition, the trigger guard protects the trigger from unintentional contact, and the sight assists in aiming. However, none of these components provide the same level of direct control over the firing action that a safety device does.