单项选择题
（）directly affect the fitness and ability of a seafarer to perform watchkeeping duties.
A.Smoking B.Drug and alcohol abuse C.Fruit D.Vegetables
单项选择题 Malacca Strait is 805 km（）and（）from 64 km in the S to 257 km in the N.
单项选择题 It is customary in shipping practice to quote freight rates（）weight or measurement,ship’s option.
单项选择题 When underway in a channel,you should keep to the（）.
