单项选择题 A propeller of 5~65m in diameter, having a mean pitch of 4~88m, turning at 72 rpm, at a speed of 11 knots (339~79m/min), will give （） of apparent slip.

单项选择题 In moving forward, a ship imparts forward motion to the water at the stems, this is known as （）.

单项选择题 Wake varies considerably with the form of the vessel, but, generally speaking, the bluffer the ship （） the wake value.