AMP - Aviation Maintenance Technician Powerplant Practice Exam

Check valve prevents oil from flowing in reverse direction. Option A, Pressure valve is responsible for regulating the pressure in the system and does not prevent oil from entering the main accessory case. Option B, Hydraulic fuse is used to prevent damage to hydraulic systems and is not related to oil flow. Option D, Oil gate is not a component in an engine system and does not serve the purpose of preventing oil from entering the main accessory case when the engine is not running. Therefore, the correct option is C, Check valve.