traction unit

例句：

1. 1.The tractor unit is responsible for pulling the heavy load.
   牵引力单元负责拉动沉重的负载。
2. 2.The tractor unit is essential for ensuring efficient farming operations.
   牵引力单元对于确保高效的农业操作至关重要。
3. 3. The tractor unit has been upgraded to improve its performance in harsh conditions.
   牵引力单元已经升级，以提高在恶劣条件下的性能。