题目选项分析

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.

The argument above assumes which of the following?

【选项】There is no systematic difference in membership between the group of mechanics who do first-time jobs and the group of those who do rework jobs.