shaft-basic system of fits

例句：

1. 1. The car'sengine is located in the center of theengine block.
   汽车的发动机位于发动机缸体中心。
2. 2. The tree's trunk isthick and sturdy.
   这棵树的树干又粗又结实。
3. 3. The machine's shaftrotates at a high speed.
   这台机器的轴以高速旋转。