Undercourse
底层, 垫层, 在花砖或瓷砖之下的底层
🗣️ 情景例句
Not really.
不是吧。
My book has a dark blue cover.
我的书有一个深蓝色的封面。
To get a full appreciation of what this means we must turn first to some recent human inventions.
要透彻理解这句话的意义，我们应先回顾一下人类最近的几项发明。