1) The global push for COVID-19 vaccination campaigns has been a significant focus, with the development and distribution of vaccines to combat the spread of the virus and protect public health.

2) In Norse mythology, the Valkyries are divine maidens who serve Odin, the chief god. They are responsible for selecting warriors worthy of entering Valhalla and escorting them to the afterlife. They are often depicted as powerful and beautiful figures, riding winged horses and wielding spears.

3) Mountains are formed through various geological processes, including tectonic plate movements, volcanic activity, and erosion.

4) The world's largest desert is the Sahara Desert in Africa, covering an area of about 3.6 million square miles (9.4 million square kilometers).