成拱形

例句：

1. 1. The bridge is made of stoneand has an arched roof.
   这座桥由石头建造，有一个拱形的屋顶。
2. 2. The old castle has a grand archway leading to the courtyard.
   古老的城堡有一个宏伟的拱门通向庭院。
3. 3. Thedinosaurs lived in aworld with many arches and tunnels.
   恐龙生活在一个有许多拱门和隧道的世界。