Now, over the last 30 years, this has been a stable migration arrangement in the world.

现在，在过去的 30 年里，这一直是世界上稳定的移民安排。

A molecule is simply two or more atoms working together in a more or less stable arrangement: add two atoms of hydrogen to one of oxygen and you have a molecule of water.

一个氧原子加上两个氢原子，你就得到一个水分子。