foam glass brick

例句：

1. 1. The bubbles on the surface of the milk are caused by air.
   牛奶表面的气泡是由空气造成的。
2. 2. The foam in the drink is a sign that it's not fresh.
   饮料中的泡沫是它不新鲜的一个标志。
3. 3. Foaming is a common problem with many types of soaps.
   泡沫是许多肥皂的常见问题。