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。