What is the phraseology for an aircraft conflict/Mode C alert?

The phraseology for an aircraft conflict or Mode C alert is designed to convey urgency and provide the pilot with clear instructions on how to respond to a potential conflict. Option B states, "Traffic alert (callsign)(position of aircraft) ADVISE you climb/descend/turn immediately," which effectively communicates critical information such as the nature of the alert (traffic alert), identifies the aircraft involved, and gives specific instructions for immediate action.

This structure helps the pilot understand both the situation and the urgency of the response required. The inclusion of the aircraft's position gives the pilot situational awareness necessary for making quick decisions to ensure safety. The directive to "climb/descend/turn immediately" is critical in helping the pilot take prompt action to avoid a possible collision, which aligns with the priorities of air traffic management.

In contrast, other options, while they do convey urgency, either do not provide sufficient details about the situation or lack the necessary clarity and immediacy expected in such scenarios, thus making option B the most appropriate choice.