Which statement is correct regarding the lift to drag ratio in straight and level flight?

The statement regarding the lift to drag ratio being at its highest value when total drag is lowest accurately reflects the principles of aerodynamics in straight and level flight. The lift-to-drag ratio (L/D ratio) is a critical measure of an aircraft's efficiency; it indicates how much lift is generated for a given amount of drag.

When an aircraft is in straight and level flight, it is achieving a balance where the lift produced offsets the weight of the aircraft. At the point where the L/D ratio is maximized, the aircraft is operating at the most efficient angle of attack where lift is maximized while drag is minimized. This relationship implies that at this optimal point, the aerodynamic design of the aircraft is such that it experiences the least total drag for the amount of lift generated.

In practical terms, pilots aim to maintain their aircraft at this optimal point during cruise to maximize fuel efficiency, as well as distance traveled per unit of fuel consumed. Understanding this relationship can guide pilots in managing their flight path and performance effectively, particularly in varying conditions of load and speed.