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

GMAT PREP question

Answer here is B My question is while means at the same time or although or whereas .
So here while means although
and why D is wrong. For but:- the first statement but second statement and second statement should new idea that is why it is wrong and better contrast can be made by while or although

in choice b, you already have the words 'at the same time'. because gmat problems don't tolerate redundancy at all, it follows that 'while' must be interpreted as meaning 'whereas'. note the following: you can correctly use 'while' with the participle (introducing), but you cannot do so with 'but'.

if you are going to use 'but', you need either a completely new clause ('...but they have also introduced), or another verb that is parallel to the verb already used ('...but have also introduced').

In option "d" can I assume that "that" wrongly refer to the nearest noun "the same time"? or it is correctly refering to chemical pollutants and only error is because we can not use participle "introducing" with but. Also pls can you explain what "at the same time" refers to?Is it adverb, conjunction etc?

the latter is correct. 'that' is totally fine here: it's followed by a plural verb ('have'), which means that it must refer to something plural. the only plural noun that fits the bill is 'pollutants'.



well, i guess you're talking about choice d. in that choice, the placement of 'at the same time' is illogical: it means that all 100,000 of the pollutants are released at exactly the same time (as in a big explosion). while that would certainly be entertaining to watch, it's obviously not the intended meaning of the sentence.

as this phrase describes the time at which an action occurred, it must be considered an adverbial phrase.

if you're asking about the meaning of this phrase in the other choices, please do reply.

I just wonder what the sentence looks like without the "reduction".

Should it be:
1. 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 that have gone virtually unregulated since they were developed more than 50 years ago.
or
2. Industrialization and modern methods of insect control have improved the standard of living around the globe while at the same time they introduce some 100,000 dangerous chemical pollutants that have gone virtually unregulated since they were developed more than 50 years ago.
or
3. Industrialization and modern methods of insect control have improved the standard of living around the globe while at the same time they are introducing some 100,000 dangerous chemical pollutants that have gone virtually unregulated since they were developed more than 50 years ago.
?

My understanding is that "while/although/whereas/etc S+V1+O1, S+V2+O2" can be rewritten to "while/although/whereas/etc V1-ing+O1, S+V2+O2" if and only if the subjects of both clauses are the same and V1 is in one of the continuous tense. In other words, #1 and #2 cannot be correct.

Am I wrong??? Just want to make sure that my concept is correct.

bump =P

I chose C! But is it guilty of an ambigous "THEY"?

The pronoun as a subject in the while clause is assumed to be referring to the subject of the main clause....at least, that's my understanding.

#1 is actually ok; there's nothing wrong with writing the sentence with absolute parallelism, provided that such parallelism doesn't change the actual meaning of the sentence.

#2 is wrong, because of the tense mismatch.

#3 is also wrong. if you're going to flesh out the participle (getting rid of the 'reduction', as you put it), you must use parallel tenses.
for instance:

while running the marathon, james tripped and fell.
unreduced --> while he was running the marathon, james tripped and fell (past tense parallelism)

timmy has learned a lot of valuable lessons while employed with the company.
unreduced --> timmy has learned a lot of valuable lessons while he has been employed with the company. (present perfect parallelism)

you get the idea.

so, if you're going to get rid of the 'reduction', then, ironically, you'll produce a sentence like #1.

Thanks Ron!

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.

If you read it carefully it cantains two parts 1.0 a main clause and 2.0 a subordinate clause . the author is saying that Industrialization has done good things at the same also time some bad things .the good thing is the main clause <Industrialization and modern methods of insect control have improved the standard of living around the globe> the bad thing is the subordinate clause ( rest of the sentence )
connect the sub to the main using while ( to express contrast ) plug in a that cluse and you will get the answer