Before extending the landing gear, it is essential to:

Before extending the landing gear, it is essential to reduce airspeed below 150 KIAS due to the aircraft's operational limits regarding landing gear deployment. Extending the landing gear at high speeds can lead to structural damage or malfunction, as the gear is not designed to withstand the aerodynamic forces and pressures encountered at higher velocities. By adhering to this airspeed limitation, pilots can ensure a safer and more reliable landing gear extension process, allowing the system to function correctly and maintain the aircraft's integrity.

The other options do not address the specific operational safety requirements for landing gear extension. Ascending to a higher altitude is not necessary for landing gear deployment; rather, gear is typically extended during descent. Increasing throttle to maximum may be counterproductive when preparing for landing, as it could lead to maintaining or increasing airspeed, which conflicts with the need to reduce speed before deploying the gear. Changing to landing configuration includes various steps, but the primary focus should be on managing airspeed to remain within safe operational limits for gear extension.