The Dvorak keyboard requires less finger movement than the ubiquitous QWERTY keyboard. As a result, Dvorak keyboard users are not only able to type more words per minute, but are also less vulnerable to both repetitive stress disorder and carpal tunnel syndrome. Nonetheless, businesses, as well as consumers, have not adopted the Dvorak keyboard. Clearly, if the Dvorak keyboard is to become more widely used, its benefits must be more widely touted. Which of the following, if true, casts the most doubt on the author's conclusion? ['Those suffering from repetitive stress injuries often attribute the injuries to multiple factors', 'Businesses have found that many employees who believe the QWERTY keyboard is responsible for stress-induced injuries are unaware of the Dvorak keyboard.', 'Many who have attempted using a Dvorak keyboard claim that learning the configuration of keys takes weeks', 'Businesses that have educated employees on the benefits of the Dvorak keyboard, have found that employees continue to use the QWERTY keyboard']