单项选择题
The horizontal flat surfaces where the upper stock joins the rudder are the（）.
A.rudder keys B.rudder palms C.lifting flanges D.shoes of the rudder
单项选择题 The grip of a joint represents the（）.
单项选择题 The fluke angle of an anchor system is the angle between the（）.
单项选择题 The fitting that allows a boom to move freely both vertically and laterally is called the （）.
