What is the approximate fuel consumed when holding under Operating Conditions O-4?

The correct choice, 1,440 lbs, corresponds to the estimated fuel consumption for holding under Operating Conditions O-4, which typically represent specific atmospheric conditions and aircraft configurations. In the context of aircraft operations, these conditions factor in various elements such as temperature, altitude, and aircraft weight, all influencing fuel burn rates.

It's essential to understand that each operating condition has a unique profile, and O-4 is defined to give a standardized measure of performance under particular parameters. The value of 1,440 lbs reflects a careful balance of the aircraft's fuel efficiency during holding patterns, which are necessary for air traffic management.

The other options present different fuel consumption values that would apply under varying conditions or assumptions. Each represents a different scenario within operational contexts. For instance, higher values might indicate either a different operating configuration or possibly a less efficient state due to factors such as increased weight or less optimal atmospheric conditions. Thus, the choice of 1,440 lbs is the most aligned with the specified operating conditions.