Hong Kong has about 40 public  beaches.  Some of the beaches are among the best in the world. People can go there for a swim. You can go to most of them by bus. To go to some beaches, you must take a boat. There are toilets, changing rooms and places to buy food and drink on most of the beaches. You will swim there without danger if you remember these instructions: 1. Never swim alone. 2. Never swim after a meal or when feel hungry or tired. 3. Do not stay in the water too long. 4. Never go out in a boat if you cannot swim. Remember: A red flag   means that it is dangerous for anybody to go into the water. A blue flag means that it is dangerous for children. It's dangerous for children to swim when you see   _  .
a red flag a yellow flag a blue flag an orange flag