1) The United States operates under a two-party system, with the Democratic Party and the Republican Party being the two major political parties that compete in elections and shape the country's political landscape.

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

3) The banking industry is regulated by government agencies to ensure the stability and integrity of the financial system and to protect consumers.

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