During an operation of a main propulsion gas turbine, the engine shuts down. Which of the following is the most probable reason for the shutdown?

Correct Answer: Option A — High vibration on the gas generator.

High vibration on the gas generator is a critical safety trip parameter. It indicates severe mechanical imbalance, bearing failure, or foreign object damage. To prevent catastrophic disintegration of the high-speed rotating assembly, the control system automatically initiates an immediate shutdown to protect the engine and personnel.