Final Answer:
Before beginning your descent on to the OLM SIX STAR, an ATC controller must issue clearance (b) N1234 descend via the Olympia 6 Arrival.
Step-by-step explanation:
The correct clearance for initiating the descent onto the OLM SIX STAR is option (b) - "N1234 descend via the Olympia 6 Arrival." This clearance instructs the pilot to follow the procedures outlined in the Olympia 6 Arrival route during the descent phase. It ensures a standardized and controlled descent path, enhancing safety and coordination with air traffic control (ATC).
In aviation, the use of standardized procedures is crucial for maintaining order and safety in the airspace. The "descend via" clearance, as specified in option (b), provides a clear and concise directive to the pilot, indicating that the descent should be executed following the lateral and vertical constraints defined by the Olympia 6 Arrival procedure. This helps in the efficient management of air traffic and ensures a smooth transition for the aircraft as it descends towards its destination.
Options (a) and (c) do not provide the specific descent guidance required for a structured arrival procedure. Option (a) focuses on a direct clearance to the OLM VOR without specifying the arrival procedure, while option (c) includes a speed instruction but lacks the necessary descent guidance. Therefore, option (b) stands out as the correct choice, aligning with standard aviation practices for descent clearances onto established arrival routes.