Which of the following methods is used for marking in a 9 line skeleton?

In the context of a 9 line skeleton, the method used for marking refers to the specific process or technique employed to pinpoint and communicate the location of targets or areas of interest to support air operations. This marking process is crucial for ensuring that friendly forces and air support can accurately identify the intended targets while minimizing the risk of fratricide.

The method of marking typically involves visual signals or other forms of indicators that are clearly understood by all involved parties. This might include smoke, laser marking, or using specific signals to delineate the area of operations. It is a standardized approach that guarantees clarity and coordination among the ground troops and the air support, thereby enhancing the effectiveness of military operations.

Other methods listed may involve different aspects of communication or observation but do not specifically address the systematic approach to marking in air-ground coordination.