单项选择题
A.every week
B.a day
C.every trip
D.a watch or once a trip，whichever is shorter
单项选择题 Functions aboard a tanker or tank barge such as connecting，disconnecting，and topping off must be supervised by（）.
单项选择题 At 0900，you take the following radar ranges: Watch Hill Point 5.4 miles; Block Island Grace Point 8.3 miles. Which statement is TRUE? （）
单项选择题 A passenger vessel is underway. When may passengers visit the pilothouse? （）