During flight, pressures on the upper and lower surfaces of the wing are _______ .
A.the same
B.not the same
C.not a factor
D.indifferent
正确答案是B
During flight, pressures on the upper and lower surfaces of the wing are _______ .
A.the same
B.not the same
C.not a factor
D.indifferent
正确答案是B