Air routes are commonly marked with which of the following?

Air routes are commonly marked with SP (Start Point), RP (Release Point), and ACP (Aerial Control Point). These designations are crucial for air assault operations as they help in coordinating and managing the movement of air assets during an operation.

The Start Point is where aircraft begin their approach to the designated area, the Release Point is where troops or equipment are deployed from the aircraft, and the Aerial Control Point is used for maintaining command and control over aerial operations. Understanding these points is essential for ensuring that air support is executed safely and effectively, maximizing the efficiency of operations.

The other options contain abbreviations that might refer to different terms or elements relevant to various military operations, but they do not specifically pertain to the common markings used for air routes. Therefore, SP, RP, and ACP are the accurate terms that signify the key points in an air assault scenario.