【单选题】
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.
查看更多
