Herbalist: Many herbal medicines work best when they have a chance to influence the body gently over several months. However, many of these herbal medicines have toxic side effects when taken daily for such long periods. Ttherefore, at least some people who use herbal medicines daily should occasionally skip their usual dose for a day or two, to give the body a chance to recuperate. Which one of the following is an assumption required by the herbalist's argument? ['At least some people who use herbal medicines daily use them for periods long enough for the medicines to have side effects.', "At least some herbal medicines work less well in achieving their desired effects if one occasionally skips one's usual dose than if one does not.", 'Some herbal medicines have toxic side effects when taken for several months, even if the usual dose is occasionally skipped for a day or two to give the body a chance to recuperate.', 'Anyone who uses herbal medicines should give those medicines a chance to influence the body gently over several months at least.']