单项选择题
Hang national flag upside down should be strictly （）.
A.prohibit B.prohibited C.prohibiting D.prohibits
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.
单项选择题 When a ship arrives at a foreign port, you should hoist （）national flag.
