单项选择题
A.prevent the towboat from sliding when the rudder is moved
B.prevent the barges from spreading out when backing down
C.hold the towboat securely to the barges
D.prevent the sidewise movement of the face barges
单项选择题 When operating in an area where sea ice and icebergs are present，which statement is TRUE? （）
单项选择题 Two vessels are abreast of each other and passing port to port in a confined waterway. What should you expect as your bow approaches the screws of the other vessel? （）
单项选择题 Topside icing that blocks freeing ports and scuppers（）.