1.   If the red lights on the dash signal danger, men go straight to the shop.

2.   Pyramiding brass signal danger.

3.   The new methods involve messenger chemicals called pheromones that are emitted by insects to attract mates, signal danger or alert fellow insects to food sources.

4.   While many animals use intricate sounds to recognize one another, attract mates and signal danger, humans have developed the richest musical repertoires of any species.