Aircraft without oxygen equipment or whose oxygen equipment is unserviceable are not supposed to fly above _______ m.
A.3600
B.4000
C.4500
D.5000
正确答案是B
Aircraft without oxygen equipment or whose oxygen equipment is unserviceable are not supposed to fly above _______ m.
A.3600
B.4000
C.4500
D.5000
正确答案是B