PrepTest 129, Section 3, Question 24
It is widely believed that lancelets—small, primitive sea(60 more words not shown)
The argument's conclusion follows logically(8 more words not shown)
- AOnly animals that(5 more words not shown)
- BSome primitive animals(12 more words not shown)
- CA vessel whose(13 more words not shown)
- DFor a vessel(15 more words not shown)
- ENo animal that(6 more words not shown)
Reading the argument
What counts as a heart? The fact that people call the lancelet's contracting vessel an artery does not settle the classification, but neither does pointing out a few similarities to hearts.
The author gives two similarities: the vessel's structure strongly resembles some other sea animals' hearts, and its muscular contractions closely resemble those of other animals' hearts. That sounds like relevant evidence. Still, what if being a heart requires another defining feature the vessel lacks? For example, if a particular chamber arrangement were required, resemblance alone might not meet that definition. We are not told that such a requirement exists; it illustrates why we need a classification rule.
What we’re looking for
The question asks us to make the conclusion follow logically. Then connect the exact evidence to the classification: any vessel with the described resemblance in structure and action is a heart. With that rule, the lancelet's vessel meets enough conditions to establish the conclusion.
Working the answers
- A
This requires an animal with a heart to have a contracting vessel. It does not say that every animal with a contracting vessel has a heart, much less that the vessel itself is a heart. Lancelets could meet this requirement without qualifying for the classification we need.
- B
Other primitive animals can have hearts without lancelets having them. The question concerns this particular vessel, not whether some primitive animal somewhere has an organ widely regarded as a heart. B also reports a belief rather than giving the needed definition.
- CCorrect
This makes the two kinds of resemblance enough: a vessel whose structure and actions closely resemble other animals' hearts is a heart. The passage already describes the lancelet vessel as meeting both conditions. Apply the rule and the conclusion follows.
- D
Muscular contractions are now required for a vessel to count as a heart, but they are not declared enough. The vessel could contract and still lack some other required feature. D answers what a heart must do, while we need a rule establishing that this vessel is one.
- E
This says an animal with a heart also has an artery. It does not tell us that an animal with an artery has a heart, or that an artery resembling a heart should be classified as one. Even accepting the existing description of the lancelet vessel as an artery leaves the conclusion unproved.
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