空泡

例句：

1. 1. The bubbles in the drink are rising to the top.
   饮料中的气泡正在上升。
2. 2. The foam on top of the milk is due to air being trapped inside.
   牛奶表面的泡沫是由于空气被困在里面造成的。
3. 3. The bubbles burst as they hit the surface.
   当气泡碰到表面时就会破裂。