flat hairspring

例句：

1. 1. The floor is flat and easy to clean.
   地板是平坦的，容易清洁。
2. 2. The table is flat and perfect for a presentation.
   桌子是平坦的，非常适合做演示。
3. 3. The road is flat and easy to drive on.
   这条路平坦，驾驶起来很顺畅。