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

2) The word "banana" contains three vowels: A, A, and A.

3) The Sahara Desert, located in North Africa, is the largest hot desert in the world, covering an area of about 9.2 million square kilometers (3.6 million square miles). It is characterized by vast stretches of sand dunes, rocky plateaus, and extreme temperatures.

4) The United Nations (UN) is an international organization founded in 1945 with the goal of promoting peace, security, and cooperation among nations through diplomatic and political means.