1) The Danube River, flowing through ten countries in Central and Eastern Europe, is the second-longest river in Europe. It has played a significant role in the cultural and economic development of the regions it traverses and is a popular waterway for river cruises.

2) The Black Lives Matter movement, which gained prominence in 2013, advocates for racial justice and equality, addressing systemic racism and police violence against Black individuals.

3) The world's first credit card was introduced in 1950 by Diners Club.

4) The Internet of Things (IoT) refers to the network of physical devices, vehicles, appliances, and other objects embedded with sensors, software, and connectivity.