In a Williamson turn，the rudder is put over full until the（）.
A. vessel has turned 90°From her original course
B. vessel has turned 60°From her original course
C. vessel is on a reciprocal course
D. emergency turn signal sound
查看答案
打孔时烧坏钻头的主要原因是（）。
A. 注水量大
B. 注水量小
C. 墙体太硬
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