对2号发动机进行大修。 A: Do an overhaul of the No. 2 engine. B: Overhaul the No. 2 engine. C: Recondition the No. 2 engine.

“ON CONDITION” maintenance conception refers to ( ). A: A check B: Borescope inspection by a fixed time C: Maintenance decision made by the engine conditions D: Overhaul by a fixed time