on ones back的用法和樣例：
例句
- Some rowing boats lay keeled over on the beach.
一些划艇船底朝天地放在沙灘上。 - His fist sent the robber sprawling on the ground.
他一拳把那搶劫犯打得四腳朝天。 - The old lady had been on her back for two months.
這位老太太已經卧病兩個月了。 - Jack could not finish his task, because he was laid on his back last week.
傑克沒能完成任務，因為上個星期他卧病在床。
