单选题The pitch of a propeller is a measure of the（）.Aangle that the propeller makes with a free stream of waterBangle that the propeller makes with the surface of the waterCnumber of feet per revolution the propeller is designed to advance in still water without slipDpositive pressure resulting from the difference of the forces on both sides of the moving propeller in still water without slip
单选题
The pitch of a propeller is a measure of the（）.
A
angle that the propeller makes with a free stream of water
B
angle that the propeller makes with the surface of the water
C
number of feet per revolution the propeller is designed to advance in still water without slip
D
positive pressure resulting from the difference of the forces on both sides of the moving propeller in still water without slip
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