on the middle还是in the middle

正确应为in the middle

释义：在中间;在中部;正忙于;

例句：

The glass cover for this is cleverly jointed in the middle.

这件东西的玻璃罩子在中间用活动接头巧妙地连起来。

When the two ends of the tunnel met in the middle they were only a few inches out.

隧道两端在中间相接时，仅有几英寸的误差。

His eyes were fixed on a small house in the middle distance.

他凝视着不远处的一座小房子。

A car alarm went off in the middle of the night.

半夜里一辆汽车的警报器突然响了起来。