1.       GWD-7-Q27:

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?

1. 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.
2. There is no
        company that successfully competes with Ace Repairs for complex repair
        jobs.
3. Ace Repairs’
        warranty is good on first-time jobs but does not cover rework jobs.
4. Ace Repairs does
        not in any way penalize mechanics who have worked on complex repair jobs
        that later had to be reworked.
5. There is no
        category of repair jobs in which Ace Repairs invariably carries out
        first-time jobs satisfactorily.