Advertisement: For sinus pain, three out of four hospitals give their patients Novex. So when you want the most effective painkiller for sinus pain, Novex is the one to choose.
Which of the following, if true, most seriously undermines the advertisement's argument?

• ASome competing brands of painkillers are intended to reduce other kinds of pain in addition to sinus pain.  
• BMany hospitals that do not usually use Novex will do so for those patients who cannot tolerate the drug the hospitals usually use.  
• CMany drug manufacturers increase sales of their products to hospitals by selling these products to the hospitals at the lowest price the manufacturers can afford.  
• DUnlike some competing brands of painkillers, Novex is available from pharmacies without a doctor's prescription.  
• EIn clinical trials Novex has been found to be more effective than competing brands of painkillers that have been on the market longer than Novex.