单项选择题
The Navigation Rules state that a vessel shall be operated at a safe speed at all times so that she can be stopped within（）.
A.The distance of visibility B.1/2 the distance of visibility C.A distance appropriate to the existing circumstances and conditions D.The distance that it would require for the propeller to go from full ahead to full astern
单项选择题 The look-out must be able（）full attention to the（）of a proper look-out．
单项选择题 She（the vessel）shall if necessary（）and in any event navigate with extreme caution until danger of collision is over.
单项选择题 SAFE SPEED is defined as that speed where（）.
