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 Earth's core is hotter than the surface of the Sun.

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) Sushi is a traditional Japanese dish made of vinegared rice combined with various ingredients, such as raw or cooked seafood, vegetables, and nori (seaweed). It is known for its artful presentation and delicate flavors, and has gained immense popularity worldwide. Sushi can take many forms, including nigiri (hand-pressed rice topped with ingredients) and maki (rolled sushi wrapped in seaweed), and is often enjoyed with soy sauce, wasabi, and pickled ginger.