雾中信号

例句：

1. 1. The airplane's engine noise is a clear signal of its approach.
   飞机的引擎噪音是它接近的信号。
2. 2.The new policy is a clear signal that the company is committed to sustainability.
   新政策是公司致力于可持续发展的明确信号。
3. 3. The sudden drop in stock prices was a clear signal that the market was overheated.
   股票价格的突然下跌是市场过热的明确信号。