Undercourse
底层, 垫层, 在花砖或瓷砖之下的底层
🗣️ 情景例句
Goodbye, it was a pleasure meeting you.
再见， 和你见面很高兴。
Are you used to the food here?
你习惯吃这儿的饭菜吗？
Carbonated drinks are acidic, and slightly safer.
碳酸饮料是酸性的，就更安全一些。