Which of the following is NOT one of the four levels of maintenance?

The answer is based on the established framework of military maintenance levels. The four recognized levels of maintenance are unit, direct support, general support, and depot maintenance.

Unit maintenance occurs at the operational level, where the equipment is maintained by operators and some basic repairs are conducted. Direct support maintenance involves more complex tasks that require specialized tools and skills, commonly provided by support teams or detachments that are forward-deployed or in close proximity to the operational units. General support maintenance serves a broader scope, allowing for repairs that are beyond the capacity of either unit or direct support levels, often including more significant overhauls and scheduled maintenance.

Strategic support is not listed among the recognized categories of maintenance levels in this context, which is why it is the correct choice as not belonging to the four levels of maintenance. This understanding is essential for ensuring efficient and effective maintenance operations within military structures.