The speed brake will retract if you perform the following:

• A. The speed brake switch is moved aft, flaps are extended, or the PCL is moved to MAX
• B. The speed brake switch is moved forward, flaps are extended, or the PCL is moved to MAX
• C. The speed brake switch is moved forward, flaps are extended, or the PCL is reduced to MIN
• D. The speed brake switch is moved forward or airspeed increases above 150 KIAS

Answer: (D)

The function being tested is how the speed brake returns to a stowed state. On this system, you can retract the speed brake by manually commanding it with the switch (moving it forward) or by the airplane’s speed logic automatically retraction when airspeed gets high enough (above 150 KIAS). These are the two reliable retraction triggers: a forward command on the switch or a high enough airspeed.

Why this choice fits best: it directly matches the known retraction triggers—manual command via the switch and automatic retraction once you exceed a speed threshold. The other options mix in conditions like flaps being extended or specific PCL positions. Those changes don’t alone guarantee retraction in this system, even though they may affect overall configuration or thrust, they don’t by themselves cause the speed brake to retract.