1) Bats are the only mammals capable of sustained flight.

2) Cyclones, also known as hurricanes or typhoons, are powerful tropical storms characterized by low-pressure centers and strong winds.

3) The fall of the Berlin Wall in 1989 symbolized the end of the Cold War and the reunification of East and West Germany.

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