How is the relationship between drag and airspeed quantified?

The correct answer focuses on the relationship between drag and airspeed, particularly in the context of how drag behaves according to the laws of aerodynamics. As an aircraft's speed increases, the drag force acting on it does not increase linearly. Instead, drag is influenced by the square of the airspeed. This means that when the airspeed doubles, the drag increases by a factor of four, which is described mathematically as drag being proportional to the square of the velocity.

This principle is crucial for understanding aircraft performance, as it shows that small increases in speed can lead to significantly larger drag forces, impacting fuel efficiency, climb rates, and overall maneuverability. Recognizing this quadratic relationship helps aircrew make informed decisions about speed management in various flight scenarios.

In contrast, the other options present misconceptions about how drag scales with airspeed. For instance, stating that drag increases less than or directly with airspeed does not capture the actual relationship dictated by fluid dynamics, and asserting that drag increases at half the rate of airspeed is inconsistent with established aerodynamic principles.