单项选择题
A.Each vessel should show sidelights
B.Each vessel should show at least one white light
C.The barges should be lighted as separate units
D.The barges should be lighted as one vessel
单项选择题 The type of fog that occurs on clear nights with very light breezes and forms when the earth cools rapidly by radiation is known as（）.
单项选择题 The two vessels underway may collide with（），if they don’t take immediate measures.
单项选择题 The term restricted visibility，when used in the Rules，refers to（）.