1) The Appalachian Mountains, running along the eastern coast of the United States, are one of the oldest mountain ranges in the world.

2) The French Revolution, which began in 1789, marked a major turning point in European history, leading to the overthrow of the monarchy and the rise of republicanism.

3) The national animal of Canada is the beaver.

4) The ozone layer, located in the Earth's stratosphere, protects us from harmful ultraviolet (UV) radiation.