Ihad traced the cause of the trouble. One of the links in the chain that drives the wheelshad snapped. After buying a new chain I was faced with the insurmountable task ofputting the confusing jigsaw puzzle together again.

　　22.I had traced the cause of the trouble.

　　因为我找到了毛病所在。

　　23.One of the links in the chain that drives the wheels had snapped.

　　驱动轮子的链条断了一节。

　　24.After buying a new chain I was faced with the insurmountable task of putting theconfusing jigsaw puzzle together again.

　　我买来一根新链条后，面临的就是如何把这些令人眼花缭乱的拼板重新组装起来。