PrepTest 103, Section 3, Question 15
A person's dietary consumption of cholesterol and fat(74 more words not shown)
The statements above, if true,(8 more words not shown)
- AThe threshold can(11 more words not shown)
- BPeople who consume(20 more words not shown)
- CPeople who consume(23 more words not shown)
- DSerum cholesterol levels(15 more words not shown)
- EPeople who consume(13 more words not shown)
Reading the argument
The line keeps rising, but it becomes much flatter. That change in pace is the important part.
Before the threshold, increased dietary cholesterol and fat produce proportional increases in blood cholesterol. Beyond the threshold, even large increases in consumption produce only gradual increases in blood cholesterol. “Gradual” doesn't mean the level stops rising completely.
Now place the average North American diet on that picture. The threshold is only one fourth of its consumption level, so the average diet is well beyond the point where the relationship changes. That doesn't mean every individual's diet is above the threshold; it locates the stated average.
What we’re looking for
For the supported conclusion, that's what I want to keep in mind: we are already past the proportional part of the relationship at the average consumption level. We can't treat the entire relationship as one straight line that rises at the same rate everywhere.
Working the answers
- A
Lowering what someone eats moves that person's consumption level. It doesn't establish that the threshold itself moves. The passage tells us where the threshold is relative to the average diet, not how to change that threshold.
- B
The average diet is already past the threshold. In that region, the passage says even dramatic increases in consumption produce only gradual increases in blood cholesterol. B predicts the dramatic rise that the stated relationship specifically tells us not to expect there.
- CCorrect
Half of the average consumption level is still above the threshold, which is one fourth of the average. For an easy picture, call the average intake 100 units. The threshold is then 25 units, and half the average is 50 units. Both 50 and 100 are in the region where added intake produces only gradual increases.
So halving the intake doesn't necessarily halve blood cholesterol. The original proportional relationship no longer applies across those consumption levels. C correctly refuses to assume that the same percentage change in food intake must produce the same percentage change in blood cholesterol.
- D
Diet is described as one of the most important factors, not the only factor. That leaves room for behavior outside diet to affect blood cholesterol. We don't need to prove what exercise or smoking does in reality; D rules out effects the passage has never ruled out.
- E
Being below the threshold doesn't establish that the person's blood cholesterol cannot fall. The proportional relationship still applies in that lower range, and nothing says a person there has already reached the lowest possible level. Other factors are also left open. E imposes a limit the passage does not provide.
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