axle analogy test machine

例句：

1. 1. The axle of the car is worn out.
   这辆车的车轴磨损了。
2. 2. The old wooden axle was replaced with a steel one.
   旧木轴被换成了钢轴。
3. 3. The axle of the train is broken.
   火车的轴断了。