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. The author’s conclusion is properly drawn if which one of the following is assumed

A. Those who seek medical care because of heroin use usually do so in the later stages of addiction.
B. Many heroin users visit hospital emergency rooms repeatedly.
C. The number of visits to hospital emergency rooms by heroin users is proportional to the incidence of heroin usage.
D. The methods of using heroin have changed since 1980, and the new methods are less hazardous.
E. Users of heroin identify themselves as such when they come to hospital emergency rooms.