1) Oprah Winfrey is an American media mogul, television host, actress, and philanthropist. She is best known for hosting "The Oprah Winfrey Show," which became the highest-rated talk show in TV history, and for her influential role in the entertainment industry.

2) Mountains are formed through various geological processes, including tectonic plate movements, volcanic activity, and erosion.

3) The assassination of Archduke Franz Ferdinand of Austria in 1914 triggered the start of World War I.

4) The concept of political stability refers to the ability of a government or political system to maintain continuity, order, and effective governance over a prolonged period, promoting social cohesion and economic development.