To ensure the bomb is safely armed, when should the timing lock be depressed?

The correct choice pertains to safely arming the bomb, specifically regarding the timing lock. The timing lock is a crucial safety feature that prevents inadvertent arming and ensures that the device is only armed when it is supposed to be. Depressing the timing lock when changing arming time settings is important because it allows the operator to modify the timing settings while ensuring that the bomb does not accidentally get armed during this adjustment phase. This action effectively maintains control over the bomb’s arming mechanism until the operator is prepared for it to be armed for the mission.

In contrast, arming the bomb prior to loading or during transportation could pose significant risks, as the bomb could become unexpectedly active. Similarly, depressing the timing lock after target acquisition implies readiness to arm the bomb, which can lead to safety hazards if the weapon is not secured. Therefore, the safest and most controlled moment to engage the timing lock is specifically when changing the arming time settings.