The four-million-year-old fossilized skeleton known as Lucy is so smal

B it is.

the idiom is "so X that Y"

The four-million-year-old fossilized skeleton known as Lucy is so small compared with many other skeleton presumed to be of same species, and so some paleontologists have argued that Lucy represents a different lineage.

A. presumed to be of same species, and so - incorrect
B. presumed to be of the same species that - correct. the skeleton is so small......that....
C. presumed that they are of same species, and so - 'they' has no referent
D. that they have presumed to be of the same species, so that - 'they' has no referent
E. that they have presumed are of the same species, and - 'they' has no referent

There's an idiom in there (not correctly completed in the original sentence): "Lucy is SO X... THAT <Y is true or Y is the case as a result>. There's no "THAT Y" in the original sentence. Eliminate A. Note the basic meaning of the nonunderlined part: Lucy is SO SMALL compared with many other skeletons... (THAT). Whatever follows "that" will have to provide the reason why we're emphasizing how small Lucy is.

Examine the other choices:
B) SO small (compared to skeletons supposedly of same species) THAT some people argue Lucy is different. Okay.
C) SO small (compared with many other skeletons presumed) THAT they are of the same species. That doesn't make sense. The Y is not true as a result of being "so small."
D) SO small (compared with many other skeletons) THAT they have presumed to be of the same species. That doesn't make sense (same reason as C). Also, this says that "they," the skeletons, have presumed something. They're skeletons; they can't presume anything. Smile
E) SO small (compared with many other skeletons) THAT they have presumed are of the same species. The idiom still doesn't work.
Only B works!

B. I chose this because when looking at the section of the sentence "is so small compared ..." this should meet and "flow" properly with the word "that." Moreover, it felt more conversational think when telling a story etc. "things were so blah blah blah THAT" The other "split" that included "that" was too wordy. GMAT would like things to be conscise; meaning don't use eight words when four will do.

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Required construction is "so small ... that"
Observe only the highlightedpart :

The four-million-year-old fossilized skeleton known as Lucy is so small compared with many other skeleton presumed to be of same species,and so that some paleontologists have argued that Lucy represents a different lineage.

Ans : C

The four-million-year-old fossilized skeleton known as Lucy is so small compared with many other skeleton presumed to be of same species, and so some paleontologists have argued that Lucy represents a different lineage.
A. presumed to be of same species, and so - idiom issue - Lucy is SO X... THAT <Y is true or Y is the case as a result>.
B. presumed to be of the same species that - Correct
C. presumed that they are of same species, and so - SO small (compared with many other skeletons presumed) THAT they are of the same species. That doesn't make sense. The Y is not true as a result of being "so small."
D. that they have presumed to be of the same species, so that - Illogical meaning - it says that the skeletons have presumed something
E. that they have presumed are of the same species, and - idiom issue


Answer B
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Compared with many other... modifies Lucy here.

Ravi

Option A: The correct idiom is ‘so… that’. This sentence uses ‘and so’ which is unidiomatic. Eliminate.

Option B: This is the best option. The usage is idiomatic – ‘the same species that’

Option C: Wrong idiom. Eliminate.

Option D: here ‘they’ incorrectly refers to ‘many other skeleton’. Also, ‘skeletons’ cannot presume anything. The meaning here is not logical. Eliminate.

Option E: Same as option D. Wrong pronoun reference. Eliminate.

Hope this helps!
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The "they" in answer choice (D) and (E) should raise some red flags when going through the answer choices. Also be careful to not fall into the immediate "Oh, I know this idiom" and thinking that an answer choice beginning with THAT has to be correct.

Some kudos would be nice! Trying to get to 200 points!
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I choose B but I want to know more about choice A

I think choice A can be correct if we say "small compared..." not " so small compared". the presence of "so" in "so small" make choice A wrong. is that right?

she is beautiful, and , so, I want to marry her.

this is correct sentence. so, choice A is wrong because of "so" in "so small". moreover, the second "so" need two comma.

we dont say
she is so beautiful ,and, so, I want to marry her.

the presence of two "so", make choice A wrong

am i correct?

Good observation!!
The following 2 constructions are used to show cause and effect.
1.So ______ that ____
2. such ______ that ___

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