PrepTest 132, Section 4, Question 17
A 24-year study of 1,500 adults showed that(60 more words not shown)
Each of the following, if(16 more words not shown)
- AThe human body(14 more words not shown)
- BBeta-carotene must be(11 more words not shown)
- CFoods rich in(16 more words not shown)
- DIn the 12-year(15 more words not shown)
- EIn the 24-year(35 more words not shown)
Reading the argument
The first study doesn't yet show that beta-carotene caused the better health. People who eat a lot of those foods might have other habits that protect them. We should keep that possibility open before treating the supplement study as a contradiction.
What we’re looking for
There are also two obvious changes between the studies: food becomes supplements, and twenty-four years becomes twelve. Perhaps the body gets something from the food that it doesn't get from the pills. Perhaps the benefit needs more time. The question is an EXCEPT question, so four answers will help explain the difference. We want the one that leaves it unexplained.
Working the answers
- A
This gives a reason the source could matter. The body processes beta-carotene in food more efficiently than beta-carotene in supplements. People could therefore benefit from eating the foods without getting a comparable benefit from the supplements. That helps reconcile the results, so it isn't our answer.
- B
If cancer prevention requires more than twelve years, the supplement study ended too soon to show that benefit. The longer food study could capture an effect the shorter study misses. This helps explain at least part of the difference; it need not account for every health outcome to be useful.
- C
The food brings other nutrients along with the beta-carotene, and those nutrients help the body absorb it. That explains why taking the isolated supplement might not reproduce the benefit of eating the food. It gives substance to the food-versus-pill difference we noticed.
- DCorrect
Having a placebo group explains how researchers compared outcomes, but it doesn't explain why beta-carotene supplements produced no health benefit. We still need to know why the food study showed better outcomes while this study did not.
Splitting participants between a supplement and a placebo doesn't mean the supplement group's benefit would disappear. Researchers could compare the two groups and detect a benefit if one occurred. D supplies a study detail without resolving the apparent discrepancy.
- E
This gives us another explanation for the food study's pattern. The high-intake group smoked less. That difference could help explain why its members were less likely to die from cancer or heart disease, even if beta-carotene itself wasn't responsible.
Then the supplement study's lack of benefit becomes less surprising: perhaps the first study's association reflected smoking habits rather than protection from beta-carotene. We don't need to invent facts about smoking in the second study to see how E weakens the apparent conflict.
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