What is one key function of the cones placed in-line with the runway centerline?

The correct answer highlights the role of cones positioned along the runway centerline, which is to assist pilots in aligning their approach with the runway. By providing a clear visual guide, these cones help ensure that aircraft are well-aligned during the critical phases of landing and takeoff. This alignment is vital for maintaining the safety and efficiency of airport operations, especially in low visibility conditions.

While the other options provide plausible functions, they do not accurately reflect the specific purpose of these cones. For instance, additional lighting pertains more to runway lighting systems rather than cones, while signaling landing procedures and indicating runway width includes broader concepts that may not be directly attributed to the cones themselves. The key function of the cones focuses specifically on aiding pilots' alignment with the runway centerline, making the correct response particularly relevant for enhancing safety in aviation operations.