名詞 red flag:

1. a flag that serves as a warning signal
2. the emblem of socialist revolution
3. something that irritates or demands immediate action

1. It's time to shake out the red flag.
   是把這面紅旗打開的時候了。
2. A red flag is a sign of danger.
   紅旗是危險的信號。
3. A red flag slowly went up the pole.
   一面紅旗徐徐升起。
4. The five-star red flag is fluttering in the wind.
   五星紅旗迎風飄揚。