Epsilon computer corporation's warranty mandates that any major

The Question asks us what could be the underlying assumption of the argument so that such conclusion could be derived from it.

What’s the conclusion? — that the difference in factory batch and repair works isn’t because the workers lack competence but because of circumstances in which these workers are performing jobs.

What does the author assume in order to draw such a conclusion? It makes sense to think that the author must be assuming that the company doesn’t have different hiring patterns for factory workers and for repairmen — that both types of workers have the same level of competence.

Now let’s negate option B. In assumption questions, if we negate an option and it weakens the argument, it’s correct.

option C on negation could be written as - “the assembly personnel are different from those who do repair jobs”
If these two kinds of workers are different then their level of competence is different, so the author’s argument that level of competence doesn’t play any role would not stand. This, argument would be weakened.

Therefore, option C is correct.

Option D is out of scope because it doesn’t establish a connect between two different types of workers in epsilon.