单项选择题
When a ship is in port, （）must keep a gangway watch.
A.officers B.crew members C.sailors D.motorman
单项选择题 When a ship is in port, the sailor on duty （）a gangway watch.
单项选择题 Hang national flag upside down should be strictly （）.
单项选择题 When you hoist national flag, you should hoist it（）.
