Eliminate A and E, because both use having at the end and create sentence passive.

Out of B, C and D, I was leaning towards D, but D is wrong because of 'but'. We use 'but', when we introduce contrast.

C is awkward.

B is correct

clock60 wrote: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

[spoiler]oa is B, my question: what is the problem with E [/spoiler]

https://www.manhattangmat.com/forums/ind ... -t460.html

This will help you out. Read carefully. Many useful points are discussed.

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

I feel it is B.

This is an example more of modifier. I removed A,C and E in the first go. In D that have is referring to same time when it should refer to chemical pollutants and so in C that is rectified and IMO it is B

hi guys
thank you for your replies. especially nicksworth for wonderful link. it helps a lot
i see now that the main problem in E is modifier issue as , + ing must refer to the subject, and initial intent od the sentence to imploy subordination clause, rather than || structure
But honestly, this sentence is not trivial one.