单项选择题
When a ship is in port, the sailor on duty （）a gangway watch.
A.has B.keeps C.looks D.takes
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（）.
单项选择题 After a ship leaves a foreign port, you should （）that country’s national flag.
