是个CR,不过是语法问题。

A significant number of complex repair jobs carried out by Ace Repairs have to be reworked under the company’s warranty. The reworked jobs are invariably satisfactory. When initial repairs are inadequate, therefore, it is not because the mechanics lack competence; rather, there is clearly a level of focused concentration that complex repairs require that is elicited more reliably by rework jobs than by first-time jobs.

看划线部分，concentration带了两个that定语从句，第2个跳跃修饰，我第一次见。偶的分析没错吧！要不就少个and,不过偶觉得逻辑经常干这种复杂句子的勾当，不加and应该也可以吧！谢谢。

跳跃修饰不错，但是我认为加and就错了，concentration在两个定从中地位不同，前者是做宾语，后者做主语，所以两个定从不是平行结构，可以将concentration that complexs repairs require中的定从和concentration之间的关系看成‘修饰词和核心词’的关系，作为一个短语，而后面的定从是修饰前面短语中的核心词。