The main ingredient in this bottle of Dr. John's Milk of Magnesia is used by nine out of ten hospitals across the country as an antacid and laxative. If this advertising claim is true, which of the following statements must also be true? I. Nine out of ten hospitals across the country use Dr. John's Milk of Magnesia for some ailment. II. Only one out of ten hospitals in the country do not treat acid indigestion and constipation. III. Only one out of ten hospitals across the country do not recommend Dr. John's Milk of Magnesia for patients who need a milk of magnesia.

The ad is a little deceptive. It tries to create the impression that if hospitals are using Dr. John's Milk of Magnesia, people will believe it is a good product. But what the ad actually says is that Dr. John uses the same ingredient that hospitals use (milk of magnesia is a simple suspension of magnesium hydroxide in water). The ad is something like an ad for John's Vinegar which claims it has acetic acid, which is vinegar. I falls into the trap of the ad and is therefore wrong. II is not inferable since there may be treatments other than milk of magnesia for these disorders. Finally, since I is incorrect, III must certainly also be incorrect. Even if I had been true, III might still be questionable since use and recommendation are not identical.