单项选择题
A.to ventilate the hold
B.to separate the cargo
C.to replace shifting boards
D.to facilitate stowage
单项选择题 When two power-driven vessels are meeting on reciprocal or nearly reciprocal courses so as to involve risk of collision,they shall be deemed to be in（）.
单项选择题 Chart/Publication correction record Card system ensures that every chart is properly corrected（）.
单项选择题 What is the distance from the bottom of a wave trough to the top of a wave crest?（）