Explanation: When making repairs or adjustments to RADAR units or any high-voltage electronic equipment, safety is paramount. High-voltage capacitors can store a significant, potentially lethal, electrical charge even after the power supply has been turned off and disconnected. This stored energy poses a severe electric shock hazard. Therefore, it is critical to discharge all high-voltage capacitors safely to ground before touching any internal components, ensuring all stored energy is eliminated. Options A, C, and D are incorrect. While fire-retardant clothing (A) may be advisable in some industrial settings, it does not address the immediate and primary electrical shock hazard from stored energy. Maintaining filament voltage (C) means the unit is still partially energized, which is unsafe when performing internal work. Reducing the magnetron voltage (D) does not eliminate the stored charge in other high-voltage components and does not make the unit safe to work on internally. The fundamental safety procedure is to de-energize and discharge.