The minimum safety altitude over a congested area is based on _______ .
A.obstacle clearance
B.altitude above mean sea level
C.altitude above ground level
D.none of the above
正确答案是A
The minimum safety altitude over a congested area is based on _______ .
A.obstacle clearance
B.altitude above mean sea level
C.altitude above ground level
D.none of the above
正确答案是A