Support The number of hospital emergency room visits by heroin users grew by more than 25 percent during the 1980s. ████████ █████ ███ ███ ██ ██████ ████ ██ ████ ███████
The argument concludes that heroin use increased during the 1980s. This is a hypothesis offered to explain the phenomenon of increased emergency room visits by heroin users in that decade.
However, the argument's support is far from perfect: there are numerous alternative explanations that could explain the rise in emergency room visits. The argument can therefore be weakened by supporting an alternative explanation, or strengthened by eliminating alternative explanations.
The author’s conclusion is properly █████ ██ █████ ███ ██ ███ █████████ ██ ████████
Those who seek ███████ ████ ███████ ██ ██████ ███ ███████ ██ ██ ██ ███ █████ ██████ ██ ██████████
The timing of emergency room visits doesn't affect the relationship between emergency room visits and heroin use overall. Even with (A), it would still be possible to give an alternative explanation for the increase in emergency room visits.
Many heroin users █████ ████████ █████████ █████ ███████████
(B) still leaves open the possibility of an alternative explanation for the increase in emergency room visits. Even with repeated visits, there could still be another reason for the increase other than an increase in heroin use.
The number of ██████ ██ ████████ █████████ █████ ██ ██████ █████ ██ ████████████ ██ ███ █████████ ██ ██████ ██████
In other words, there's a strict correlation between emergency room visits and heroin use. This is our sufficient assumption: it guarantees that an observed increase in emergency room visits corresponds to an increase in heroin use. There's no room for alternative explanations now.
The methods of █████ ██████ ████ ███████ █████ █████ ███ ███ ███ ███████ ███ ████ ██████████
(D) may strengthen the argument by eliminating the possibility that heroin use has directly become more dangerous, but it doesn't eliminate all possible alternative explanations. That makes (D) insufficient to guarantee the conclusion.
Users of heroin ████████ ██████████ ██ ████ ████ ████ ████ ██ ████████ █████████ ██████
How emergency room staff know that someone is a heroin user isn't relevant to why that person is visiting the emergency room in the first place. In other words, the reliability of the statistic cited in the argument doesn't affect how we explain that statistic. (E) doesn't prevent alternative explanations.