Over mountainous region and plateau area the safe altitude along air route is _______ m，above the highest elevation within 25KM on each side of the centre line of the air route.
A.1000
B.600
C.300
D.400
正确答案是B
Over mountainous region and plateau area the safe altitude along air route is _______ m，above the highest elevation within 25KM on each side of the centre line of the air route.
A.1000
B.600
C.300
D.400
正确答案是B