What are the pre-fire safety checks for the 120mm mortar?

The correct answer involves a comprehensive set of pre-fire safety checks for the 120mm mortar. This includes verifying mask and overhead clearance to ensure there are no obstructions that could pose a safety risk when the mortar is fired. Additionally, checking the cannon locking mechanism is crucial to ensure that the mortar functions properly during operation. Pre-fire safety checks are vital to confirm multiple aspects of the equipment and environment to prevent accidents, ensuring that the mortar can be fired safely and effectively.

Other choices may suggest limited checks that could overlook critical aspects of safety. For instance, solely focusing on mask clearance or just the buffer housing assembly would not provide a complete assurance of operational safety. Ensuring that the cannon is always elevated, while important during firing, does not encompass the broader range of checks necessary for safe operation.