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) The Amazon Rainforest, located in South America, is the largest tropical rainforest in the world, covering an area of approximately 5.5 million square kilometers (2.1 million square miles). It is known for its exceptional biodiversity and plays a crucial role in the global ecosystem.

3) The world's largest species of shark, the whale shark, can reach lengths of up to 40 feet (12 meters) and weigh over 20 tons.

4) The word "oxygen" contains two vowels: O and E.