retractable undercarriage

例句：

1. 1. The new car has a retractable roof that can be opened and closed quickly.
   这款新车有一个可伸缩的天窗，可以快速打开和关闭。
2. 2.The tent is retractable, so it can be folded up easily when not in use.
   这个帐篷是可伸缩的，所以不使用时可以轻易折叠起来。
3. 3.The robotic arm is retractable, allowing it to move around the room without being seen.
   这个机器人手臂是可伸缩的，允许它在房间内移动而不会被看到。