center of surface

例句：

1. 1. The center of theearth is a fascinating place to visit.
   地球的中心是一个令人着迷的地方。
2. 2. The center ofgravity is the point where an object willfall down if it were to be removedfrom its support.
   重心是物体从其支点移除时将下落的点。
3. 3. Thecenter of the room is where the tableand chairs are placed.
   房间的中心是桌子和椅子放置的地方。