a bubble of oxygen的用法和样例：
- We moderns think in a bubble of about ten years.
- There was a shortage of oxygen at the top of the mountain.
- A bubble will burst at the slightest touch.
- Used to create a bubble of air around the caster's head. Often used to allow the caster to breathe underwater.
- A molecule of water consists of two atoms of hydrogen and one atom of oxygen.