The cross bus tie relay automatically opens, isolating DC bus 1 from DC bus 2, under the following condition（s）:
A.A.At glide slope capture during a flight director or autopilot ILS approach. This isolates the DC busses during approach to prevent a single failure from affecting both navigation receivers and flight control computers
B.B.Provide more power to the AC STANDBY Bus
C.C.A or B
正确答案是C