The number of hospital emergency room visits by heroin users grew by more than 25 percent during the 1980s. Clearly, then, the use of heroin rose in that decade. Which one of the following, if true, would account for the statistic above without supporting the author's conclusion? ['Many hospital emergency rooms were barely able to accommodate the dramatic increase in the number of medical emergencies related to drug abuse during the 1980s.', 'Viral and bacterial infections, malnourishment, and overdoses account for most hospital emergency room visits linked to heroin.', 'Heroin use increased much more than is reflected in the rate of heroin-linked hospital emergency room visits.', 'Widespread use of automatic weapons in the drug trade during the 1980s raised the incidence of physical injury to heroin users.']