Which of the following load factors apply when flaps are up?

When analyzing the load factors that apply when flaps are retracted (or up), the correct range is indeed from -1.0G to 2.5G. This range signifies how the aircraft can safely handle various loads during flight under normal conditions without the influence of high drag that flaps introduce.

When the flaps are up, the aircraft's structural integrity is designed to accommodate a negative load factor (which occurs during maneuvers like upsets where the aircraft could experience a momentary negative G) up to -1.0G, and it can also handle positive loads up to +2.5G, which is especially important during maneuvering or turbulence. This range is crucial for pilots to understand for operational safety, ensuring that during flight scenarios, they remain within the aircraft's structural limits.

The other answer choices reflect incorrect load factor ranges for the configuration when flaps are retracted, primarily because they either understate or overstate the extremes of load factors that the aircraft can safely encounter. Understanding this load factor range is fundamental for pilots to maintain optimum control and safety while flying the CRJ 900.