PrepTest 143, Section 4, Question 20
Many important types of medicine have been developed(62 more words not shown)
Which one of the following(7 more words not shown)
- AThere are substances(26 more words not shown)
- BMost of the(20 more words not shown)
- CThe majority of(25 more words not shown)
- DAny substance of(22 more words not shown)
- EThe tropical rain(25 more words not shown)
Reading the argument
Couldn't we discover the same useful chemical somewhere else?
I can see why unexplored rain-forest plants might matter to medicine. We have found useful substances in plants before, and more species remain to be studied. Destroying them could remove a valuable route to new treatments.
But “will never be developed” goes further. What if scientists discover the same chemical in a laboratory or another source? Losing one route to a medicine doesn't automatically eliminate every route. My initial prediction for the required assumption would address that concern: these plants must offer something we would otherwise miss.
What we’re looking for
Let's keep the task precise. A required assumption doesn't have to repair every weakness. It has to be something this reasoning needs. The choices may expose a different missing piece from the one I noticed first.
Working the answers
- ACorrect
Unstudied plants aren't necessarily sources of undiscovered substances. Several plants could contain the same medicinal chemical. We might not have studied every plant even though we had already discovered all the useful substances they contain.
A rules out that possibility by saying some unstudied plants contain medicinal substances different from the ones already discovered. Without anything new left to discover in them, the move from “we haven't studied these plants” to “losing them means losing future medicines” falls apart.
This isn't exactly my initial prediction about other routes to discovery. A doesn't establish that a laboratory could never find the same substance, and it doesn't resolve every concern about the conclusion. It supplies another assumption the argument needs: the unexplored plants offer more than repeats of what we've already found.
- B
The argument doesn't require valuable rain-forest plants to grow elsewhere. If they do, that could provide another source and reduce the need to preserve this environment to find them. B doesn't have to be true for the argument to work, and its emphasis on other locations points away from the claimed dependence on rain forests.
- C
Why must a majority be useful? Suppose only 10 percent of the studied species supplied valuable substances. That could still represent important medical discoveries and a reason to think more are possible. The argument doesn't need more than half of studied species to contain such substances.
- D
Preserving the possibility of discovery doesn't guarantee success. Scientists could study a plant and still miss a useful substance. The argument doesn't require every medicinal substance eventually to be discovered; it claims some important medicines will be lost if the forests aren't preserved.
- E
This is a recommendation to preserve the forests. The argument's conclusion instead predicts a consequence if they aren't preserved. Someone could accept that consequence while disagreeing about what should be done. A policy judgment isn't required for the stated prediction.
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