Final answer:
The correct cruising altitude range for non-RVSM aircraft from FL290 to FL600 is in multiples of 4000 feet, not represented by any of the given airspeed options.
Step-by-step explanation:
In aviation, when it comes to cruising altitudes, there is a concept called Reduced Vertical Separation Minima (RVSM). RVSM allows aircraft to operate at a reduced vertical separation, which enables more aircraft to safely fly at the same altitude. For altitudes below FL290 (Flight Level 290), the cruising altitudes are determined by the International Civil Aviation Organization (ICAO) and are typically in 2,000 feet increments. However, for altitudes from FL290 to FL410 inclusive, the cruising altitudes for non-RVSM aircraft are every 4000 feet. So, the correct cruising altitude range for non-RVSM aircraft from FL290 to FL600 would be in multiples of 4000 feet. None of the given options of 120 knots, 180 knots, 250 knots, and 320 knots represent cruising altitudes, as knots refer to airspeed, not altitudes.