Which of the following describes a spotting of "LINE"?

The concept of "LINE" in the context of artillery and fire support refers to the position of an impact relative to the observer and the target. When a round is said to have impacted "on line," it indicates that the impact point aligns directly with the line of sight between the observer and the target, meaning that the observer sees the round land precisely where it needs to be in accordance with their intended aiming point. In this case, "on line" conveys that the round successfully falls in the desired area as perceived from the observer's position. This term is crucial for ensuring accurate artillery support and communicating adjustments effectively during fire missions, confirming that the strike is neither to the left nor right of the intended line but rather directly on the intended trajectory.