单项选择题
A.back current from the rudder
B.greater pressure on the right or left side of the propeller，depending on rotation
C.lower pressure on the right or left side of the propeller，depending on rotation
D.torque from the velocity and angle at which the surrounding water impinges upon the propeller blades
单项选择题 Shell plating that has curvature in two directions and must be heated and hammered to shape over specially prepared forms is called（）.
单项选择题 Panting frames are located in the（）.
单项选择题 No deduction is allowed for the（）mess-room in ships having passenger accommodation，which are not also provided with a passengers’ mess-room.