a signal of distress的用法和样例：
- The ship was flying a signal of distress.
- A red light is usually a signal of danger.
- The position about halfway up a mast or pole at which a flag is flown as a symbol of mourning for the dead or as a signal of distress.
- To leave suddenly,often as a signal of disapproval.
- A red light is a signal of danger.
- A signal of disaster or destruction.