单项选择题
A head on situation shall be deemed to exist at night when a power-driven vessel sees another power-driven vessel ahead and （）.
A.one sidelight and the masthead light are visible B.the vessels will pass closer than half a mile C.both vessels sound one prolonged blast D.both sidelights and masthead light(s) are visible
单项选择题 The Sailing Directions contain information on （）.
单项选择题 You will find information about the duration of slack water in the （）.
单项选择题 （）amplify charted detail and contain information needed for safe navigation.
