Grow-Again ointment is a proven treatment for reversing male hereditary baldness. Five drops daily is the recommended dose, and exceeding this quantity does not increase the product' s effectiveness. Ttherefore, offering a manufacturer' s rebate on the purchase price of Grow-Again will not increase sales and consequently would be unprofitable for the manufacturer. Which one of the following, if true, would most strengthen the argument? ['When using an ointment, people tend to believe that applying it in greater quantities can make it more effective.', 'Grow-Again is a product whose per-unit manufacturing cost does not fall significantly when the product is produced in large quantities.', 'The rebate, if offered, would not attract purchasers who otherwise might not use Grow-Again.', 'Grow-Again is more effective on some of the men who use it than it is on others.']