1) 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.

2) The first modern health insurance policy was introduced in Germany in the late 19th century.

3) The process of photosynthesis, performed by plants, algae, and some bacteria, is responsible for producing the oxygen we breathe.

4) The first successful mass-produced personal computer, the IBM PC, was introduced in 1981 and played a significant role in popularizing the use of computers in homes and offices.