backburner

例句：

1. 1. The backburneris a crucial part of the engine's operation.
   备用发动机是引擎运行的关键部分。
2. 2. The engineer had to replace the backburner before the race began.
   在比赛开始前，工程师必须更换备用发动机。
3. 3.The team decided to use the backburner as a last resort in case ofengine failure.
   团队决定在引擎故障时使用备用发动机作为最后的手段。