For what reason has heroin use escalated?
A. Users first started abusing prescription opioid pain relievers but discovered heroin was cheaper.
B. Users started out abusing prescription opioid pain relievers but found heroin gave them a more intense high.
C. Today's heroin is more potent than the heroin of years past, but more of the drug is necessary to get the same high.
D. Needles used for injecting heroin are more available today than in years past and are manufactured with anti-HIV virus protection.
E. Users can be certain of the purity of today's opium and do not have to worry about finding impurities and containments in the drug.