PrepTest 104, Section 4, Question 6
Monarch butterflies spend the winter hibernating on trees(57 more words not shown)
Which one of the following(11 more words not shown)
- Athe amount of(17 more words not shown)
- Bthe amount of(14 more words not shown)
- Cthe amount of(16 more words not shown)
- Dthe proportion of(21 more words not shown)
- Ethe proportion of(8 more words not shown)
Reading the argument
Taking people into the forest to protect butterflies sounds helpful, but could the visitors disturb the habitat they're trying to save? The next sentence gives us a reason to worry: the tourists trample most of the small shrubs.
Then comes the important qualification. Those shrubs are necessary for butterflies that fall off the trees. How many butterflies actually fall? If almost none do, destroying the shrubs might affect very few butterflies. If nearly all do, losing those shrubs could put much of the population in danger. The argument needs a connection between damage to the shrubs and danger to the population.
What we’re looking for
We're asked what would be useful to know in evaluating the argument. Turn that concern into a question: what proportion of the hibernating butterflies fall? A proportion is especially useful because it tells us how widespread the problem is. Knowing that ten butterflies fall wouldn't tell us much without knowing whether there are twelve butterflies or twelve million.
Working the answers
- A
This concerns habitat the butterflies aren't currently using. Knowing that other suitable forests exist doesn't tell us whether the tourists are endangering the butterflies in the forests they do use. We'd need further information about whether and how the butterflies could move there before using that land as an answer to the specific shrub problem.
- B
How much wood is cut could matter to assessing the woodcutters' harm. But the conclusion under review is that the tour groups themselves endanger the butterflies. Even if woodcutting is a serious threat, that doesn't settle whether trampling these shrubs poses an additional threat. The amount cut leaves our central question unanswered.
- C
This shifts attention to plants that aren't necessary for the butterflies' survival. Imagine the tourists also crush some grass or flowers. That might be a separate environmental concern, but it doesn't tell us whether the butterflies depend on the shrubs being destroyed. We need to evaluate the particular path from trampled shrubs to endangered butterflies, not count every kind of plant damage.
- D
This tells us how the woodcutters' activity is distributed across forests. Perhaps a large share of their trees comes from butterfly habitat, or perhaps only a small share does. Either way, we still don't know how often butterflies fall and need the shrubs. As with B, information about the woodcutters doesn't resolve the stated concern about the tourists.
- ECorrect
Test the two possible answers. If no hibernating butterflies fall, the loss of shrubs needed by fallen butterflies supplies no reason to think this population is in danger. If most fall, destroying most of those essential shrubs gives us a much stronger reason to worry. That is why knowing the proportion would help evaluate the argument.
This doesn't mean a small proportion would make every death unimportant, or that zero falls would prove tourists can cause no other harm. It tells us whether the particular evidence offered supports the particular danger claimed.
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