I thought that after "but" you should put a clause.

I'd like to know why the structure Subj + verb, but + present participle is correct in this case and a similar structures are not correct such as in this GMATPrep sentence

Industrialization and modern methods of insect control have improved the standard of living around the globe while at the same time they have introduced some 100,000 dangerous chemical pollutants, having gone virtually unregulated since they were developed more than 50 years ago.

a. while at the same time they have introduced some 100,000 dangerous chemical pollutants, having
b. while at the same time introducing some 100,000 dangerous chemical pollutants that have
c. while they have introduced 100,000 dangerous chemical pollutants at the same time, and have
d. but introducing some 100,000 dangerous chemical pollutants at the same time that have
e. but at the same time introduce some 100,000 dangerous chemical pollutants, having

OA is B
I found the Ron's explanation here saying that if you use but you need either a new clause or a parallel verb.

industrialization-and-modern-methods-usage-of-while-and-but-t1871.html

What is the difference between the two problems? Is it that in the first problem but + present participle modifies the next clause, whereas in the second problem but + gerund does not produce a valid clause?

I'd appreciate if someone could clarify
Thank you in advance.

nah. you aren't parsing this correctly.

the -ING participle here is not related to the "but" construction; it's part of an extra modifier. here's the reduced sentence, with that modifier changed to yellow:

Galileo did not invent the telescope, but on hearing, in 1609, that such an optical instrument had been made, he quickly built his own device from an organ pipe and spectacle lenses.



the first problem doesn't have "but + present participle", so you're addressing a problem that doesn't actually exist.

--

by the way, it is possible to have "but + present participle" -- if there's another present participle to which this one can be parallel.
for instance:
two feet of snow blanketed the city, paralyzing commerce and traffic but creating beautiful scenery.

Got it. Thank you very much.

no problem

The posts here helped me a lot on this problem. Thanks!

Since I didn't realized the major problem (such as the even though changed the relationship), I was bothered on some other splits and wondering whether those are valid consideration.

1. Is it acceptable to split the idiom "heard of" as "heard, in 1609, of" regardless other errors pointed out in this thread?

2. While (C) has those errors explained in the thread, I want to know whether the structure itself (without the "he" at the end) is acceptable as "Galileo (subject), even though + clause, quickly built (verb) ... ", such as in some situation that the meaning is appropriately conveyed?

yep.
in fact, that would be the best place to put "in 1609" in that sort of context -- right next to "heard", the action that actually took place in 1609.



eeeeeeeeeeeehhhhh

i don't think that would be strictly incorrect, but it's just plain awful -- that's a horrible place to put that subordinate clause.
this is one of those constructions that isn't technically 100% incorrect, but is so bad that gmac would almost certainly not write a correct answer in that style. (i.e., any answer choice containing this format will probably also contains some other sort of error.)

if one were to write a sentence with that sort of construction, that sentence would probably appear with the subordinate clause out front, so that "galileo" could be reunited with the rest of its own clause:
even though xxxxxxxx, galileo quickly built ...

D changes the meaning - he didn't build a telescope "even though" he didn't invent it. "Even though" indicates some kind of cause-effect connection. The original sentence is just telling us - he wasn't the inventor but he did build one soon after its invention.


can u explain this with examples

hemant, take a look at Stacey's further explanation of the "even though" and let us know if you have more questions.

_________________
Jamie Nelson
ManhattanGMAT Instructor

thanks

:-)

_________________
Jamie Nelson
ManhattanGMAT Instructor

Ron,

i think my understanding of the bolded modifier below is misguided. It appears to me that it is a prepositional modifier modifying "hearing". I initially thought "hearing" was a verb, so then "in 1609" would be a adverbial prep modifier. But in that case, why the commas around it? no where in the MGMAT SC guide does it mention a non-essential verb modifier.

Galileo did not invent the telescope, but on hearing, in 1609, that such an optical instrument had been made, he quickly built his own device from an organ pipe and spectacle lenses.

perhaps "hearing" is a gerund? then in that case, is "in 1609" a noun modifier of the noun(gerund) hearing? then the commas indicate that it is non-essential?

i know this seems a bit overkill for this sentence, but i've seen some tricky modifier problems that really exploit ambiguity/meaning when you have a string of modifiers .. one after another, sometimes with commas, sometimes without

dave, if you are interested in assigning a grammatical role to “hearing” in this sentence, note that it follows the preposition “on”.
the only things that can be the objects of prepositions are nouns (or pronouns), so it follows that “hearing” is functioning as a noun (= gerund) here.

--

as far as the essential/nonessential distinction -- a couple of comments:
1/ many -- perhaps even most -- modifiers can be either essential or nonessential.
2/ i have never seen an actual, official gmat question whose solution requires the essential/non-essential distinction.

therefore, you should probably avoid this distinction in looking for criteria on which to eliminate choices.
in many cases, the modifier could legitimately be written either way -- in these cases, it's just a semantic choice, based upon how “essential” the author feels that the modifier is. this sentence is one of these cases: the commas around “in 1609” indicate that the author is marking this information as interesting, but not particularly important.

here's another example of what i mean (although, honestly, this is really not a topic on which you should waste much of your time):
my father told me, only three years ago, that i am an adopted child. --> here, the commas indicate that the timeframe is an interesting bit of context but isn't essential to the message that i'm trying to convey.
my father told me only three years ago that i am an adopted child. --> here, the lack of commas indicates that the timeframe is an important part of the point i'm trying to make (as in “oh my gosh, why would he wait so long to tell me?”)

ultimately, though, the final verdict on this distinction is that it really doesn't matter much. unless you specifically learn that a modifier has to be essential or nonessential -- or that it has fundamentally different functions in those two roles (like comma -ING vs. no comma -ING) -- you should probably assume by default that it could be either.

thanks Ron that example nailed it. Trying to make everything fit into the rules I read in the guide, I got confused.

as for your example, i'm certain i've seen gmat problems (which I can't post here), that add another level of complexity to it. I just bolded another modifier I threw in.

my father told me, only three years ago, and without emotion, that i am an adopted child. <-- sounds fine to me, a series of adverbial prepositional modifiers modifying "my father told". is this OK? is the "and" incorrect?

my father told me, in 1999, which is an odd numbered year, that i am an adopted child.

<-- i've seen this construction in an answer choice before where the bolded verb modifier is modifying the object of the preposition 1999. "in 1999" itself is an adverbial prep modifier. I tend to eliminate these answer choices because a much less awkward one exists, but i end up with this nagging feeling since I don't know why I considered it wrong.

aside from one issue, these both look okay, although probably more complex than you'd see (or be willing to deal with) on the GMAT. the one issue i see is that you should remove the comma in front of the bold "and" in your example. let me know if this answers your questions..

_________________
Tim Sanders
Manhattan GMAT Instructor

Thanks Tim, yes that answers my question. I also thought the "and" is strange joining two adverbial prepositional phrases.