Q24 - It is widely believed that lancelets

[hunter108]

Can someone help to explain to me why (C) is wrong?

If the definition in (C), that a vessel whose structure and actions closely resemble those of other animals is a heart, is assumed, then how can it fail to force the conclusion that the lancelet's vessel is a heart?

Thank you.

[bbirdwell]

If the definition in (C), that a vessel whose structure and actions closely resemble those of other animals is a heart, is assumed, then how can it fail to force the conclusion that the lancelet's vessel is a heart?

Exactly! This is why (C) is the correct answer. Might wanna check your answer sheet...

[vik]

The latest ten LSATs book I bought says D is the right answer

[alinanny]

The latest ten LSATs book I bought says D is the right answer

THIS!
I am very confused!

[ManhattanPrepLSAT1]

So there is no confusion. The correct answer for this question is (C). Sorry vik... Either you misread your book, or there is a bad version of this test going around.

vik, where did you get your copy of this test? Let's get down to the bottom of this.

But for all you readers, answer choice (C) is definitely the correct answer. Answer choice (D) limits what could be considered a heart, and would offer no support for what qualifies as a heart, and instead could only be used to disqualify something from being a heart.

Answer choice (C) however perfectly bridges the gap in the argument. The evidence states that lancelets have vessels with a structure similar to that of hearts in other sea animals and that perform the same action as hearts in other animals. It concludes then that these vessels are hearts.

Let's just look at some of the other answers.

(A) would limit what would have a heart to certain animals, but would offer no support for whether lancelets did have a heart.
(B) has several issues. What is widely to be a heart and what is a heart are two separate issues. And secondly, these are animals other than lancelets, so who cares?
(D) limits what could be considered a heart, and so could be used to say what doesn't have a heart, but not what animals do.
(E) limits what could be considered to have heart, so could be used to eliminate some animals from having a heart, but would not guarantee that any animal has a heart.

The central issue with the three most tempting (but wrong) answer choices (A), (D), and (E) is that they all put having a heart or what can be considered to be a heart on the wrong side of the conditional.

We want, "if something looks like a heart or performs the function of a heart, then it is a heart." These answers say, "if something is a heart, then ..." That's reversed logic!

Hope that helps!

[vik]

I bought the latest book of tests 52-61 from LSAC last week. I just took at the answer again. It is clearly marked D in the book!

[ManhattanPrepLSAT1]

Haha! Good to know. You might want to let the LSAC know that they have a typo in their book. In other copies they have released, and I have now checked this answer against several sources to confirm, but answer choice (C) is definitely correct.

[sge4]

Phew! Had same problem. I wish this were the answer to all my missed questions! Thanks, Matt.

[jamiejames]

I have in my hands a book that has all the questions sectioned by type, and C is credited as the correct answer. When I opened this Webpage and read that C was wrong I thought my entire thought process would have to be re-done, thank goodness :

[Rendona001]

Can someone provide the logic chain for this question? Or am I wrong to draw out a logic chain for this question? If I am wrong what is the correct way to attack this question?

[ohthatpatrick]

With Sufficient Assumption, after reading the paragraph once, I jump into logically unpacking the conclusion to figure out
1. what do I need to prove
2. what terms are in the conclusion?
3. have these terms been defined / attached to other concepts in the Evidence?

CONCLUSION:
This vessel is a heart

To prove that claim you would typically need two ingredients:
1. If you are XYZ, then you are a heart.
2. This vessel is XYZ.

So did we get either of those ideas?

We get some #2 info, but we never define what it means to be a heart.

What do we know about this vessel?
it resembles the heart structure of other sea animals
and
its muscular contractions closely resemble those of animal hearts

Since we were given two details about "this vessel", either one could give us a correct answer.

You could prephrase:
"If it resembles the heart structure of other sea animals, then it's a heart"
or
"If its muscular contractions are like those of animal hearts, then it's a heart"

(And, of course, you anticipate that, because it's Sufficient Assumption, the correct answer may be written in contrapositive form)

(A) says "If you have a heart ---> contracting vessel". We need a rule that says "If you're XYZ, then you're a heart"

(B) is not a universal definition of a heart

(C) This looks like our first and second prephrase combined.

(D) This, like (A), is not useful, because it starts "IF you're a heart ---> XYZ"

(E) Similarly, this says "IF you have a heart ---> XYZ"

[DevorahK415]

Could you say that D is an illegal reversal? Until you said it was like A, I did think it was proving what was a heard (what C is doing) but in reverse. Just want to be very clear on why D is wrong. Thanks!

[Laura Damone]

Yep, D is an illegal reversal. If it were reversed, it would tell us that any vessel that undergoes muscular contractions is a heart, and that would prove the argument's conclusion. Nice work!