staircase of open-well type

例句：

1. 1.The stairs are narrow and winding.
   楼梯狭窄且曲折。
2. 2. She climbed the stairs to reach the top floor.
   她爬楼梯到达顶层。
3. 3.The old man used to climb the stairs every morning to exercise.
   这位老人以前每天早上爬楼梯锻炼。