PrepTest 155, Section 2, Question 15
Few, if any, carbonated beverages contain calcium.(77 more words not shown)
Which one of the following,(6 more words not shown)
- ATeenagers who drink(19 more words not shown)
- BTeenagers engage in(23 more words not shown)
- CSome teenagers have(10 more words not shown)
- DSome of the(13 more words not shown)
- EThe more calcium(21 more words not shown)
Reading the argument
Maybe these teenagers are breaking bones because of what they're doing, not because of what they're drinking.
The proposed explanation is plausible. Caffeine makes people excrete more calcium, and a calcium deficiency can make bones brittle. That could connect caffeinated drinks with broken bones. But a plausible route doesn't establish that it is the primary explanation for the pattern we see.
What if the teenagers drinking lots of these beverages are also the teenagers doing more extreme sports? Imagine a group that likes energy drinks and also spends more time skydiving or doing other risky activities. Their activities could account for more broken bones, even if caffeine weren't the main reason. That's a hypothetical alternative, not a claim about what energy-drink customers actually do.
The comparison matters: we're comparing teenagers who drink large amounts of caffeinated carbonated beverages with teenagers who don't. To explain the difference, we'd want something that differs between those two groups.
What we’re looking for
For the weaken question, I expect another possible cause of the higher injury rate. Riskier activities would work if the answer connects them to the relevant drinkers. But we should stay open to a different alternative that also challenges the caffeine explanation.
Working the answers
- ACorrect
This takes a different route from my risky-activities prediction. The heavy drinkers consume fewer calcium-rich beverages. Perhaps they are getting too little calcium in the first place, rather than mainly losing extra calcium because of caffeine. Think of choosing an energy drink instead of a calcium-rich drink such as milk: the missing calcium could matter independently of caffeine's effect. A gives us another relevant difference between the two groups, so the author has less reason to single out caffeine as the primary cause.
- B
This is tempting because it mentions exactly the sort of risky activity we considered. But compare the groups. B says teenagers do more risky things than older and younger people. Our argument compares one group of teenagers with another group of teenagers. Even if teenagers as a whole face greater injury risks, that doesn't explain why the heavy caffeinated-beverage drinkers have more broken bones than other teenagers. We need a difference within the teenage group.
- C
Caffeine doesn't have to be the only possible source of calcium deficiency for it to be the primary explanation of this particular pattern. Some teenagers who consume no caffeine could have deficiencies for other reasons. That doesn't tell us why the heavy drinkers have more broken bones than the comparison group.
- D
The caffeine content of a less popular beverage doesn't establish anything about the cause of these teenagers' injuries. We aren't trying to identify which drink has the most caffeine. We need information bearing on why one group suffers more broken bones.
- E
Greater calcium intake can go along with greater calcium excretion. That doesn't tell us whether someone is left with too little calcium, and it doesn't establish a relevant difference between the teenage groups. We still need evidence connecting an alternative explanation to the higher injury rate.
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