Though the remains of some of the oldest hominid specimens have almost

OFFICIAL EXPLANATION





• HIGHLIGHTS

Meaning?

Although the remains of some specimens have almost turned to stone because minerals have invaded the bone,
most [of the remains] either are not mineralized or are only partially mineralized.

1) SO, a word that can substitute for a word, phrase, or clause, means "mineralized." I discuss the word so below.
2) the words some and most mark off groups that are different. Whatever this "only partially" idea is in the options belongs with the "most" group. Members of the some group are a disaster. Members of the most group are not a disaster or are only a partial disaster.
-- some of the remains are like stones because the bones have been mineralized,
but
-- most [of the remains] are not like stones because the bones are not [at all] mineralized or the bones are only partially mineralized.

THE PROMPT

• some and most are the subjects, plural, of the sentences, plural (two sentences exist)

• Most are not ruined [mineralized] or are only partially ruined [mineralized] makes sense.

Most are not mineralized, __________[something about partly or partially]
A) only partially are so
B) only in part
C) only partially
D) or only in part
E) or are only partially so

Whatever goes in that blank is tied to the subject "most."
The placement of the missing language suggests that it belongs with the group "most."
The logic of the options—some quality is "only in part"— places the answer with the subject "most."
(Both not mineralized and partially mineralized stand in heavy contrast to the first sentence, in which "some" are a near-total disaster).

All of the pairings in the options use only and some form of partially. "Only partially"? Meaning?
"Only partially" means no more than partially mineralized, or slightly mineralized.

• Split #1: we need a conjunction

We need a conjunction because the two subgroups of most have different characteristics; we need a conjunction to join the adjective phrases that describe the two subgroups.
(Jargon: We need a conjunction because the subject "most" has two subject complements that are alternatives, i.e., that do not co-exist.)

-- Most are not mineralized (at all)
or
-- are mineralized only partially.

We have no way of giving the subject most its two subject complements (not X, slightly X) without a conjunction.
Wrong: Most are not [at all] mineralized, only partially mineralized.
Correct: Most are not [at all] mineralized, or are only partially mineralized.

Eliminate options A, B, and C because they all lack the conjunction or.

• Split #2: Parallelism

D) . . . most are not mineralized, or only in part.
Huh? "Or only in part" has no clear meaning.
→ X and Y should be parallel and are not.
X = are not mineralized
Y = only in part

Check E.

E) . . . most are not mineralized, or are only partially so.
X = are not mineralized
Y = are only partially mineralized [so]
That option works.

Eliminate D.

The correct answer is E

• NOTES

USE THE STRUCTURE OF THE SENTENCE

Even if you did now know that "so" meant "mineralized," the structure of the sentence could have helped you choose E.
Though signals contrast.
Contrast requires at least two things.
Contrast means that one group or object will have characteristics that are different from the other group or object, or that the two groups will do something in contrasting ways.

Most is a new subject, and as predicted, "most" are different from "some."
The end-of-sentence placement for "only partially" strongly suggests that the characteristic belongs with the group "most," not the group "some."

Whether you whittled the answers down to A and E or to D and E, the next question would have been: is this answer parallel?
Options A and E give clues that "only partially" needs a verb.
Neither option A nor option D is parallel to the language in the prompt.

Because we have a not in "Most are not mineralized," we must repeat the verb are in order to avoid the "not."

Wrong: The berries are not ripe or only partially. Nonsense.
Correct:The berries are not ripe or are only partially ripe.
Correct: The berries are not ripe or are only partially so.

Parallelism is one of the basics in SC (along with S/V agreement, pronoun agreement, and complete sentences).

The word SO

The word SO can substitute for a word, phrase, or clause in English.

He was very angry, and he told me so. SO = was very angry
I'm going to London next week, or at least I hope so. SO = that I am going to London
You shouldn't really stop work before six, but you can do so today. SO = stop work
Examples taken from here

So can stand in for an adjective, as it does in this sentence.
Most are not mineralized or are only partially so.
Some of the oil paintings are partly dry, but others are completely so.

You may see do so, does so, and did so on the GMAT.
Do/does/did can substitute for almost any verb (two exceptions), and so can substitute for almost any phrase.

Commas
The comma before are only partially so is not standard.
When a subject has a compound predicate (two verbs), typically we do not put a comma before the second verb.
Except in the case of a comma splice, do not let a comma be the reason for eliminating an option.
If you are thinking about commas for more than 10 seconds, you are thinking too much about commas.

Writers cannot be completely consistent about commas.
Commas are used to mimic speech patterns or to clarify a sentence..
In this case, the sentence is clearer and thus better with the non-standard comma.

COMMENTS

From everything I've read on this thread, you all had very good instincts.
Okay, so the question took some of you a little while.

Next time that you get stuck, maybe you will stop for 5 seconds, take a breath, and ask, "Am I missing any basics?"
Parallelism is one of the basics.

Don't get stuck on comma usage (except: no comma splices and use the Oxford comma to help you figure out how many items are in a GMAC list).
(Every expert who has commented on commas says the same thing as I. We sound like broken records.)

Another basic: the word OR is usually a parallelism marker.

This question is hard. Nice work.