The __________ detent on the flap/slat handle is used for takeoff.

The correct answer indicates that the ½ detent on the flap/slat handle is specifically used for takeoff configuration. In aircraft operations, particularly for the C-17, the ½ position allows for a balanced configuration of flaps and slats, which is crucial for generating the necessary lift during takeoff while also ensuring stability.

Using the ½ detent strikes a balance between enhancing lift and maintaining aerodynamic efficiency, which is ideal as the aircraft transitions from ground to air. This detent is designed to provide optimal performance by allowing for a moderate increase in lift without unduly increasing drag, thus supporting a safer and more effective takeoff.

The other options represent different configurations that do not align with standard takeoff practices for the C-17. The UP/RETR detent would be inappropriate for takeoff as it has the flaps and slats retracted, which reduces lift substantially. The 0/RETR configuration, where flaps are retracted and slats extended, is not suitable for takeoff either since it doesn't provide sufficient lift augmentation. The FULL detent, while providing maximum lift, may introduce significant drag and control challenges, making it less favorable for standard takeoff procedures.