Sentence Correction

Jatinder wrote:The question discussed in the following link needs further discussion
https://www.beatthegmat.com/sc4-t21945.h ... acdbf2cd00

I am typing the question below as requested by Stacey

Aerugo, also known as verdigris, is the green bloom visible on many copper items, and is produced, like iron rust, over the course of time by the exposure of the metal to the oxygen in the atmosphere.

a) visible on many copper items, and is produced
b) that is visible on many copper items, and which produces
c) visible on many copper items, and produces
d) that is visible on many copper items, and that produces
e) which is visible on many copper items, and which produced

I chose E

Doubt: the oficial answer A violates the comma rule: If the subject does not appear in front of the second verb,
do not use a comma.

(I have seen the rule is maintained in the OG questions such as Q 81 (Yellow book OG11))

Pls explain in detail. Should i keep this rule in mind while attacking the questions or not ?

Stacey Koprince wrote:In general, I don't base answers on commas because the test doesn't officially test us on comma placement. The comma placement can sometimes give us a valuable clue about the intended sentence structure (is this a modifier or a list or a compound verb or whatever?), so I use commas in that sense, but I focus more on grammar than punctuation to eliminate answers (except for semi-colons and colons).

Here's our structure:
Subject, (aside), verb object + descriptor, and verb, (aside), prep phrases

The reason there's a comma before that "and" is to indicate that this verb should match with the subject, not with the descriptor given for the object.

that is: it's not trying to say "is the green bloom visible on items and (is the green bloom) produced by blah blah blah"

rather, it's trying to say "Aerugo is X, and (Aerugo) is produced by Y."

Let's look at the other options:
B: Aerugo is the bloom that is visible, and (Aerugo) which produces... no
alternatively: Aerugo is the bloom that is visible, and (the bloom) which produces... no
C: Aerugo is the bloom visible, and (Aerugo) produces... no, it doesn't produce itself
D: Aerugo is the bloom that is visible, and (Aerugo) that produces... no
alternatively: Aerugo is the bloom that is visible, and (the bloom) that produces... no (again, doesn't produce itself)
E: Aerugo is the bloom which is visible, and (Aerugo) which produced... no
Aerugo is the bloom which is visible, and (the bloom) which produced... no

So A is the only one that works.
The moral of the story: don't eliminate based on commas unless you have nothing else to do. Deal with grammar first.

Stacey Koprince wrote:Yes to giving lower priority to comma rules. Semi-colons and colons you can give the same priority as grammar, but commas have a lot more flexibility.

I still would've chosen A, even given your suggested revision.

I agree that "Aerugo" and "the bloom" are interchangeable from a meaning standpoint, so that's not why I'd still eliminate E (with your suggested changes).

I'd eliminate it for two reasons:
1) noun modifiers introduced by "which" should have commas before them, and this one wouldn't; since I know the GMAT hews to that particular comma rule, I would be skeptical of a choice that didn't use "comma which"
2) when you use "which" to introduce a noun modifier, the general intent is that the info in that modifier is extra info, unnecessary to the primary meaning of the sentence. You should be able to take out any info in a "which" modifier and still understand the primary meaning of the sentence (even if you lose the extra meaning given in the modifier).

Aerugo is the green bloom. Do I still get the main meaning of the sentence? This is always a little bit arguable, but in this case I would argue: no. The green bloom of what? What's a green bloom? Is Aerugo a flower? Maybe I'm looking at a green flower and a red one and someone says - Aerugo is the green one.

vs. Aerugo is the green bloom visible on many copper items. Yep, that gives me the primary meaning. I know what the sentence is talking about now.