The company concludes that a 90-day inventory buffer will prevent any production stoppage caused by a delay in board shipments. That conclusion holds only if no shipping delay can outlast the 90-day cushion.
Choice A reports that several past shipping delays affecting board deliveries have each lasted considerably longer than 90 days. If delays of that length have happened before, the same could happen again, and once a delay exceeds 90 days the buffer runs dry before new boards arrive, causing exactly the stoppage the company claims it has prevented. This directly undercuts the conclusion, so A is the answer.
Choice B concerns the supplier's factory capacity, which affects how fast the supplier can manufacture boards, not how long a shipping, customs, or carrier delay might last once boards have left the factory; it does not threaten the buffer. Choice C raises the storage fee's cost, but the conclusion is about whether the buffer prevents a stoppage, not about what the buffer costs, so a cost detail cannot weaken a reliability claim. Choice D describes what other appliance makers do, which says nothing about whether this company's own buffer can be exhausted. Choice E concerns a different part, plastic housings, from a different supplier, which falls entirely outside the conclusion's scope of stoppages caused by a delay in board shipments.
Only choice A attacks the link between the 90-day buffer and the promise that it prevents any stoppage.