rust of alfalfa

例句：

1. 1. The old car's engine has a lot of rust on it.
   这辆旧车发动机上有很多锈。
2. 2. The metal surface is covered in rust.
   金属表面覆盖着锈。
3. 3. Rust can be caused by exposure to water and oxygen.
   锈是由于暴露于水和氧气而引起的。