Final answer:
The primary responsibility for separation of VFR aircraft when in radar contact lies with the pilot, adhering to the 'see and avoid' principle, although ATC may provide assistance with traffic advisories when possible.
Step-by-step explanation:
When flying under Visual Flight Rules (VFR) and in radar contact with Air Traffic Control (ATC), the primary responsibility for separation between aircraft in most cases falls to the pilot. According to aviation regulations, VFR flight relies on the principle of 'see and avoid,' which means pilots must maintain vigilance to detect other aircraft and adjust their flight path accordingly to avoid collisions. While ATC may assist with traffic advisories when workload permits, the final responsibility rests on the pilot. Furthermore, when operating in congested areas, known as Class B, C, or D airspace, or when receiving flight following services, ATC does provide separation services between VFR and IFR traffic, but the pilot still maintains the responsibility for visual separation from other VFR traffic.