1) As of 2023, the COVID-19 pandemic continues to impact countries worldwide, with efforts focused on vaccination campaigns, public health measures, and economic recovery.

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

3) The development of the microprocessor by Intel in 1971 paved the way for the modern computer and led to the exponential growth of computing power.

4) 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.