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.

A    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.

B   There is no
     company that successfully competes with Ace Repairs for complex repair
     jobs.

C    Ace Repairs’
     warranty is good on first-time jobs but does not cover rework jobs.

D    Ace Repairs does
     not in any way penalize mechanics who have worked on complex repair jobs
     that later had to be reworked.