Chef: This mussel recipe' s first step is to sprinkle the live mussels with cornmeal. The cornmeal is used to clean them out: they take the cornmeal in and eject the sand that they contain. But I can skip this step, because the mussels available at seafood markets are farm raised and ttherefore do not contain sand. Which one of the following is an assumption required by the chef's argument? ["The chef's mussel recipe was written before farm-raised mussels became available.", 'Mussels contain no contaminants other than sand.', 'The mussels the chef is using for the mussel recipe came from a seafood market.', 'Sprinkling the mussels with cornmeal does not affect their taste.']