hollow axle

例句：

1. 1.The tree was hollow when I saw it.
   当我看到那棵树时，它很空心。
2. 2. The house was hollow and empty inside.
   这所房子里面空荡荡的。
3. 3.The hollow sound of the bell echoed through the hall.
   钟声空洞地在大厅里回响。