When does the amber DUAL BLEED Light illuminate?

A.A.When the APU bleed valve is open.

B.B.When the APU bleed valve is open and the No.1 engine bleed switch is ON.

C.C.When the APU bleed valve is open, the No.2 engine bleed switch is ON and the isolation C.valve is closed.

D.D.When the APU bleed valve is open and the No.1 engine bleed switch is OFF.

正确答案是B

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