What is meant by the phrase in 1900 europeans believed the world was their oyster?

polisit can also mean a body of citizens. in modern historiography, polis is normally used to indicate the ancient greek city-states, like classical athens and its contemporaries, and thus is often translated as "city-state". the body of citizens came to be the most important meaning of the term polis in ancient greece.

in londan the most because it was one of the growing countries