Despite Hong Kong historically being part of China and being inhabited by Chinese people, that drastically happened in the last century. Hong Kong got into the hands of the European colonial powers, and even after they left the area, they didn't left Hong Kong. The reason why the presence in Hong Kong was kept was because of its excellent strategic position.
The newly formed nation had excellent ports and excellent location. It was quickly industrialized. That led to rapid economic growth. The economic growth and the prosperity of the small nation made, as well as it deep connections with the Western World, attracted lot of people to move in it. The Chinese population is still dominant, but over time people from all over the world moved in, thus the ethnic structure of this nation changes significantly, to a point where now it has citizens from pretty much every corner of the world.
Answer:
volcanic outgassing - carbon dioxcide
comets and meteoroids - icy debris
major component of modern atmosphere - nitrogen
