I want to know what are Subgroup modifiers, how they function,how they are created & how they are tested on GMAT.
As per Manhattan GMAT
Subgroup Modifiers- When you want to describe a part of a larger group with a modifier, use one of the following three Subgroup Modifier constructions.
Right: This model explains all known subatomic particles, SOME OF WHICH WERE only recently discovered.
Wrong: This model explains all known subatomic particles, SOME OF WHICH only recently discovered. - Why this sentence is incorrect or why verb is required after WHICH
Right: This model explains all known subatomic particles, SOME OF THEM only recently discovered. - Why this sentence is correct even though verb is not present after them.
Right: This model explains all known subatomic particles, SOME only recently discovered. - Why this sentence is correct.
Wrong: This model explains all known subatomic particles, OF WHICH SOME WERE only recently discovered.- Why this sentence is incorrect.
Hope you don't mind taking time to explain these concepts.
With Regards, Fame
One of the strengths of MGMAT is that they are hyper-thorough about everything. In a way, a weakness of this approach is that they can get you to worry about something that's not particular common. I would estimate that if you took 20 GMATs in a row, you would only see "sub-group modifiers" once or twice. It's just not that common.
First of all, what is a subgroup modifier? Suppose the main clause of a sentence is talking about some large group ---- the Japanese, the auto industry workers, sea mammals, small towns in the US Midwest, the integers, the elements on the Periodic Table, verbs in the French language, Oscar-winning movies, etc. etc. ---- any large group of anything. Suppose the main clause says something about this large group in its entirety, and we want to make a further clarification either about the whole group or about some part of the group ----
1) All German people are blah blah blah, but some of them are blah blah blah.
2) Blah blah blah migratory birds, most of which are blah blah blah.
3) Blah blah blah subway trains in NYC, all having blah blah blah.
Those underlined phrase are examples of grammatically correct sub-group modifiers --- modifiers which talk about either part of the whole group (as in #1 & #2) or which add further clarification to the whole group (#3).
Keep in mind, first of all, that in any of these, the "part" word could be any of what MGMAT calls the SAMAN words (some, any, none, all, more, most
) or any quantity word (many, few, each, both, either, neither, half, one,
Now, what's going on with the different grammatical structures following these?
The words "which" and "who" & "whom" are relative pronouns --- these have to introduce a full [noun]+[verb] clause --- in fact, the relative pronoun will act as the noun in the clause, so it must be followed by a bonafide verb.
4) I admire firemen, few of whom would do X
. = correct ("whom" is followed by a bonafide verb)
5) I have a low opinion of NY Yankees fans, many of whom doing X
. = incorrect ("whom" + participle is not complete)
6) I read a book about Chinese dynasty, most of which lasted blah blah blah
. = correct. same as #4
7) The city council took an extensive survey of houses in Berkeley, none of which having blah blah blah
. = incorrect, same as #5
By contrast, suppose instead of a relative pronoun, we want to use an ordinary pronoun, "them" --- "some of them", "all of them", "most of them", etc. ---- now, this phrase is a noun, and we have two options(a)
an absolute phrase = [noun + participle](b)
a coordinating conjunction (e.g. "and", "or", "but", etc.) and another independent clause = [noun] + [verb]
8) She wrote her dissertation on mollusks, some of them growing blah blah blah.
= correct, absolute phrase
9) The Protestant Churches believe blah blah blah, but some of them also believe blah blah blah.
= correct, two independent clauses, correctly joined by a coordinating conjunction.
10) The winner carried Ohio in all president elections since 1964, two of them involved a major third-party candidate
. = incorrect, run-on sentence = tow independent clauses not properly joined by a conjunction.
The foregoing should explain why the correct sentence in the MGMAT are correct. Now, let's look at the sentences MGMAT cites as incorrect:
11) The Standard Model explains all known subatomic particles, of which some of them were only recently discovered
. = Two pronouns = redundant. Basically you have a [noun][noun] structure, as in "My friend he is intelligent
." This occurs in colloquial speech, but it is incorrect in formal speech and never will be acceptable on the GMAT.
12) The Standard Model explains all known subatomic particles, some of them which were were only recently discovered
. This has the incorrect structure [independent clause][noun][modifier], as in "The store is open, the street which was recently paved.
" = nonsense. That's the problem with this one.
13) The Standard Model explains all known subatomic particles, some of which only recently discovered
. = same mistake as #5 & #7 above.
Notice the general format [independent clause][noun][modifier] can be correct if the noun is an appositive phrase
modifying something in the sentence, such as
14) Lincoln was a noble man, a president who guided the country through wa
r. = the noun "president" is an appositive, modifying either "man" or "Lincoln."
The problem, though, is that a subgroup ("some of them", "most of them", etc.) can never be an appositive for the whole group, which is why this otherwise acceptable structure is illegal in this context.
BTW, the "model" discussed in the MGMAT example sentences is known in Particle Physics as "the Standard Model", which is why I included this in the sentences.
Does all this answer your questions?
Magoosh Test Prep