Advertisement: We at Vesuvius Vacuums always give our customers what they deserve, and the

y deserve the very best. That's why we use only SuperTec air filters. Which of the following, if true, would most undermine the argument expressed in the advertisement？

A．In a test of three leading air filters, the SuperTec air filter performed at the same level as one of the filters and at a higher level than the other.

B．The SuperTec air filter is the only kind of air filter that will fit in the model of vacuum sold by Vesuvius Vacuums.

C．In a national study by a prominent consumer group, Vesuvius Vacuums gained a "superior" rating for product quality.

D．The customers of Vesuvius Vacuums have expressed no preferences concerning the type of air filter used in the product.

E．The specific air filter used in a given vacuum makes only a small difference in the long-term performance of that vacuum.