Columnist: Computer voice-recognition technology currently cannot distinguish between homophones such as "their" and "there. " As a consequence, until voice-recognition technology is improved to recognize and utilize grammatical and semantic relations among words, voice-recognition programs will not accurately translate a computer user ' s spoken words into written text. Which one of the following is an assumption required by the columnist's argument? ['Computer programs that check the spelling and grammar of written text are currently able to distinguish between homophones.', 'Unless voice-recognition technology can distinguish between words that are homophones, it cannot recognize grammatical and semantic relations among words.', 'Humans can distinguish between homophones without using information about the grammatical and semantic relations among words.', 'In order for computer voice-recognition technology to distinguish between homophones, it must be able to recognize grammatical and semantic relations among words.']