Mo2men wrote:An analysis of tree bark all over the globe shows that chemical insecticides have often spread thousands of miles from where they were originally used.

A. that chemical insecticides have often spread thousands of miles from where they were originally used
B. that chemical insecticides have spread, often thousands of miles from their original use
C. chemical insecticides, having often spread thousands of miles from where they were used originally
D. chemical insecticides, often spreading thousands of miles from where their original use
E. chemical insecticides, often spreading thousands of miles from where they were originally used

OA: A

[spoiler]In choice incorrect B,

1- what is the effect of delaying 'often'???

2- Does 'their original use' have different meaning??[/spoiler]

"Where they were originally used," refers to the place where the insecticides were first used.

""Their original use," refers to what the insecticide were used first used for. This is problematic for two reasons. First, it doesn't make sense to discuss the distance from a type of use, rather the distance from a place. Second, it sounds as though the insecticides were once used for one purpose and are now used for a different purpose. Not the intended meaning.

Mo2men wrote:An analysis of tree bark all over the globe shows that chemical insecticides have often spread thousands of miles from where they were originally used.

A. that chemical insecticides have often spread thousands of miles from where they were originally used
B. that chemical insecticides have spread, often thousands of miles from their original use
C. chemical insecticides, having often spread thousands of miles from where they were used originally
D. chemical insecticides, often spreading thousands of miles from where their original use
E. chemical insecticides, often spreading thousands of miles from where they were originally used

I received a PM requesting that I comment.

B: miles from their original use
It is illogical to discuss the distance from a USE.
Eliminate B.

C, D and E: An analysis shows...chemical insecticides.
Conveyed meaning:
An analysis shows the EXISTENCE of chemical insecticides.
Not the intended meaning.
According to the original sentence, an analysis shows not the insecticides themselves but what the insecticides HAVE DONE:
An analysis shows...that chemical insecticides HAVE OFTEN SPREAD.
Eliminate C, D and E.

The correct answer is A.

OA: Chemical insecticides have often spread thousands of miles from where they were originally used.
Here, the portions in blue are RESTRICTIVE MODIFIERS that circumscribe how chemicals insecticides have spread.
They have spread in ONE PARTICULAR WAY:
often...thousands of miles from where they were originally used.
In the OA, it is possible that chemical insecticides have not spread in any other way.

B: Chemical insecticides have spread, often thousands of miles from their original use.
Here, the portion in red is a NON-RESTRICTIVE MODIFIER that does NOT circumscribe how chemical insecticides have spread.
As a result, the core of the sentence -- the portion in blue -- conveys that chemicals insecticides have spread IN GENERAL .
In other words, chemical insecticides have spread not in one particular way but in MANY WAYS.
The modifier in red merely conveys one of the many ways in which chemical insecticides have spread:
often...thousand of miles from their original use.

Since the meaning conveyed by the original sentence -- that chemical insecticides have spread in one particular way -- is logical, eliminate any answer choice that does not convey this meaning.
Eliminate B.

GMATGuruNY wrote:

Mo2men wrote:An analysis of tree bark all over the globe shows that chemical insecticides have often spread thousands of miles from where they were originally used.

A. that chemical insecticides have often spread thousands of miles from where they were originally used
B. that chemical insecticides have spread, often thousands of miles from their original use
C. chemical insecticides, having often spread thousands of miles from where they were used originally
D. chemical insecticides, often spreading thousands of miles from where their original use
E. chemical insecticides, often spreading thousands of miles from where they were originally used

B: Chemical insecticides have spread.
Conveyed meaning:
Whereas chemical insecticides once covered a relatively small fraction of Earth, they have since SPREAD, with the result that they now cover a much GREATER fraction of Earth.
Not the intended meaning.
The intended meaning is conveyed by the OA:
Chemical insecticides have often spread thousands of miles from where they were originally used.
Here, it is unknown whether insecticides now cover a large portion of Earth.
Rather, the conveyed meaning is simply that -- in many cases -- an insecticide can be found thousands of miles from where it was first used.

Dear Mitch,

The part in red does not show the difference of meaning, compared to the OA. Can you please make clear of meaning of B. I feel both have same meaning.

Thanks

Mo2men wrote:Can you please make clear of meaning of B. I feel both have same meaning.

Please revisit my post above, in which I've clarified the difference in meaning between the OA and B.