The ARPA may swap targets when automatically tracking if two targets __________.

The Automatic Radar Plotting Aid (ARPA) is designed to track multiple targets and provide crucial information for collision avoidance and navigation safety. When two targets pass close together, the ARPA system may confuse or "swap" the targets because they are at a similar position on the radar screen. This can lead to errors in tracking and representation since the system may misinterpret signals from the two closely spaced targets.

The close proximity can create an overlapping of target return signals, making it difficult for the ARPA to determine which target is which consistently. This is particularly critical in scenarios where accurate tracking is necessary to avoid collisions. By recognizing that swapping targets can occur under these conditions, navigators can take additional precautions, such as manually identifying targets or adjusting the radar settings to improve tracking accuracy.

In contrast, the other options do not typically lead to target swapping under normal circumstances. For example, targets on reciprocal bearings or the same bearing would still maintain their unique identifiers unless their proximity causes confusion, and targets at the same range might be adequately distinguishable based on speed or directional movement. Thus, the scenario of targets passing close together presents the highest risk for target swapping in ARPA systems.