Which MK 64 machine gun cradle assembly provides travel lock and mechanical fire control adjustment capability?

The choice indicating the train and elevation assembly is correct because this component of the MK 64 machine gun cradle assembly is specifically designed to facilitate adjustments for both horizontal (train) and vertical (elevation) movement of the weapon. It incorporates mechanisms that allow shooters to lock the machine gun in place securely and adjust fire control mechanically, which is crucial for accurate targeting and stability during engagements.

These functionalities ensure that the operator can efficiently aim and fire the weapon while maintaining control over its positioning. The train and elevation assembly effectively enhances the versatility and operational readiness of the machine gun system.

In contrast, the other components, such as the base assembly, elevator assembly, and locking assembly, do not encompass the combined capabilities for mechanical fire control adjustments as effectively as the train and elevation assembly, thus making it the appropriate choice for this particular question.