plain combustion chamber

例句：

1. 1. The plain design of the dress is very classic.
   这件衣服简单大方的设计非常经典。
2. 2. The plain truth is that she doesn't like him.
   事实就是她不喜欢他。
3. 3. The plain wooden table was a welcome addition to the room.
   这个朴素的木桌子是房间的一个受欢迎的添加。